Gold as a result. Is that extra Gold a big deal? For certain! Is the bonuses from the UB worth it in the capital when it would otherwise be unavailable? Definitely! Regarding other cities, you can settle wherever necessary and you will still build this UB. We're not talking about a terrible building that people feel like is optional. The bonuses, especially the extra 
Culture and Gold for Temple, Amphitheater and Garden, can definitely be felt. While it's true Sweden doesn't go Tradition unless someone does it for fun, the bonuses aren't as weak as you seem to be suggesting. 
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I think you underestimate the power of having this UB available for all cities. Let's talk about the capital city. If you settle off river and fresh water, you get +1
Is this UB the weakest? Maybe you can give some examples because I don't know all the Classical Era UB off the top of my head.
In addition, this isn't a huge nerf. Imagine how often you get Tundra starts and/or Lakes nearby compared to other starts. Basically, we are, as you stated, making it so it's more consistent for all games instead of certain starts being really broken. Will people feel that bonus removed? They might if they get the perfect start but they more than likely won't even notice.
As for there being no Sweden is OP threads, that's a good thing. We don't want an OP civ. Therefore, the suggestion of making them even better isn't justified. Sweden had good and bad games in my playthroughs. When I play them, I can feel their entire kit being quite balanced with no time when they are really weak. Why are we giving this UB more yields when no one complained and the nerf won't be felt for most of our games?
is delayed and regular Baths have it meaning it's not impossible for Sweden to have access to it regularly, and you'll in most cases only get all this in medieval outside of super productive cities as you won't be getting an Amphitheatre/Garden/Temple before that (Garden's not available before Theology anyway).
It being worth it doesn't make it a real unique building. In most unique building cases, you want them built ASAP. Remove the Science and replace it with nothing and it's good, but nothing to change your plans over - if you have river heavy start, then the UB's power over the replacement is almost non-existent. That is NOT the case for Floating Gardens or Nilometer, which'd both outyield this one quite heavily. It is a nerf to a civ that doesn't need it. If you feel they're balanced now which you do admit, why nerf them for no reason? The RNG-based yields can just be changed to be reliable - worse than if in the optimal case, better than in the worst.
You ask why give this UB more yields when all I want is a change in how they're given so it stops being RNG-based, and I ask - why are we taking away yields from this UB when no one complained at it's strength and the nerf will be felt in every single one of our games, assuming you don't play a map without any lakes or tundra around? Even an average Sweden that doesn't start near Tundra's going to be losing tens of Science over it and prioritising expansion there, while being lame and weird, means you get a super-Science city. Of course, it's far weaker than if you started on Tundra or near a huge Lake, but you will feel it anyway, it'll just be something instead of carrying you. In both cases it'll feel wrong as it isn't what a warmongerer should be doing. Right now if I don't spand there, I'd definitely expand to decent-sized Tundra which typically also has enough sustaining resources just to get this Science, so yes - this nerf will be most assuredly felt, and it'll be very harsh.
On the other hand, if I start near Tundra now, I expand in the Tundra further knowing that I will be rewarded for doing so. Similar occurs with big lakes, or even smaller ones - as Sweden, they're prioritised and fought over. My gameplan changes because I can potentially receive more Science from this city than I will from my capital in late classical. You cannot honestly expect me to believe I, who sometimes play Sweden, won't feel the change when it was such a strong, UB-carrying feature, that I changed my decisions based on it's very existence, and while claiming that you also admit the civ is balanced as it is now. I felt the yields, I did things I wouldn't otherwise to some degree based on it every Sweden game, so your post just cannot resonate with me because it's wrong. What I hated was that where you start impacted it greatly - and just giving it stronger base yields while cutting out the terrain dependency, or changing it's features, would make it closer to okay. Right now it's too RNG-focused. It ranges from okay to bordering on broken, all depending on the map, and that isn't fun. There's too many map RNG lottery civs already, what with Siam (what CS you start near determines everything), Inca (self explanatory), Polynesia (to a degree), etc. While the Science per lake/Tundra is potentially mighty and it changes my gameplan, it doesn't do it in an experience-enriching fashion is what I'm trying to say.
To add to the previous points, I'll reiterate that the only complaints I remember in this thread were that the Swedish uniques are weak. There's very many civs in vanilla that, just like Sweden, nobody complains about being OP that got TWO good or very good uniques here, so why should Sweden in 4UC get two additional ones that would as a result be arguably worse than China's 4UC which people sometimes do complain about being OP? Even Songhai has superior 4UC uniques.
The UB isn't the weakest now, but after this nerf it'd be as it's only strong advantage would be being buildable outside of fresh water areas which, while nice, won't help on many starts and maps. You say your desired nerf to a civ you consider balanced wouldn't be felt on most maps, but Bastu as a whole wouldn't have any noticeable impact on just as many maps.The +3
We have discussed this before. It is not intended. Please post the bug on the github
(scaling with era?) per birth instead of 15%, that will never amount to that much. It might get crazy, though, and there's quite a few yields per birth mechanics.. If not enough, remove maintenance too, or improve 
as well. Simple, straightforward.. The amount of such uniques is increasing though, maybe not the best idea.
keep in mind that the choices of bonuses are, to the best of our ability, tied to the actual history, usage, etc. of the IRL building. Bastu got their tundra/lake bonus because I felt that was flavourful and relevant to the building.
per 3 Tundras - of course they shouldn't be compared, but the UB favours certain terrain too much, overincentivising it. 1 per 2/3 Tundra/Lake tiles worked, with a base yield of 1/2 (+ something?) or something else would reduce the impact of RNG, if that's even possible.
i think this strikes a fine balance. We can certainly reduce the power difference between tundra by making it 1 for 2 tiles. I’m not sure if we can do the same for lakes, since lakes are a feature subcategory unto themselves, but it might be possible. They are rare enough that a fullI think Bastu's a bit too RNG/start based right now, though. The bonus's too big and determines the power of the UB a lot by how you start. Compare it to Caravansary's 1
per tile shouldn’t be a problem unless you are using specific map settings.
Starts with the Trailblazer I promotion.
Starts with the Lost Codicies (receive 5
Has moreCombat Strength (6 vs. 5).
Has no combat penalty vs. Barbarians.
Combat Strength, up from 5, and no damage penalty against Barbarians. Now, the AI doesn’t really go around slamming their Pathfinders into Barbarians, nor does anyone else for that matter, and the Holkan does not succeed well enough at doing so anyway. So the Holkan, at best, survives specific situations where it otherwise would have gotten killed by barbs. These two bonuses alone are underwhelming to say the least. As a result, in games without Ancient Ruins, the Holkan provides very little, if any, tangible benefit to high level AI players. King+ AI Mayan opponents are essentially playing with 3 Unique Components to everyone else’s 4 (or Venice’s 5 but they deserve the extra one for obvious reasons).
to lake tiles per 2 worked tundra or river tiles
The way I see it is that the Shoshone's ability to choose the reward they get from Ancient Ruins is a minor cherry on top of their UA that exists largely for flavor. Sure, they are impacted at least a little bit by disabling Ancient Ruins, but the Civ is still very much playable in both the hands of the player and the AI. The Mayan Holkan, on the other hand, basically becomes a standard Pathfinder in the hands of the AI assuming Ancient Ruins are disabled (although I would argue that it still works in the hands of the player).
