Regarding culture victory, adding a condition to it that either all civs must have adopted either your ideology or are following your religion (in case you haven't founded one).
Having this condition would effectively mean a domination victory. The AI has very little issue with happiness thus it is virtually impossible to flip them from their ideology unless you vassalise them and it is virtually impossible to flip a founder civ to another religion unless you capture their holy city at least so they can't produce inquisitors, which apart from the odd exceptions will be their capital.
The issue with culture victory at the moment is it is actually more of a culture victory.i.e. it is a race to who get the two level 3 tenants rather than who can gain influencial on all civs as that seems relatively easy to achieve. It also seems that you have no real defense against enemy tourism as the levels of tourism are so high so your onlt defense really is conquest or getting a culture victory first as all other victory types except domination are more heavily gated and effectively impossible to achieve until right at the end of the game.
In the past, if you had a large empire you could counter tourism with high culture output to at least slow down someone going for tourism but in a recent example i wasn't going full domination but ended up having around 30 cities and 5-6 vassals providing me with large amounts of culture also and even with focusing on every culture building and buff i could i couldn't even slow do tourism pressure and i had to make the decision to launch a naval invasion on Arabia as we entered the Atomic era who were already dominant with everyone and were only waiting for their last social policy to be able to win the game even though they had both been sanctioned so no trade routes were allowed and travel ban was enacted as well as me making sure that i didn't allow them any other buffs by not trading open borders and pumping culture so no buff to them from boredom in my empire.
As i wanted to understand the updated tourism game i played a tourist victory myself and i feel that the change to the way the empire debuff to tourism from cities is possibly a significant part of the issue. In a way i like that you can have a bigger empire and go for tourism, especially as you kind of need a reasonable size empire to at least be able to defend yourself against agressors and if your too small you just end up in endless defensive wars throughout the game but it does mean there is a huge chunk of additional tourism flying around, around 25-50% from an average size civ.
In this game i was influential will all civs on my continent before we even found the other continent and again it became a culture race in the end with 3 civs being dominant with everyone, myself who was going tourism victory, Portugal who likely got influencal off the back of my religion and Morroco who went from nowhere to overtaking me to the point i was actually getting unhappiness from their cultural pressure which i assume is mostly down the Kasbahs and and the additional tourism they would get on building hotels etc as this is when their tourism exploded so i guess this was accidental rather than intended as they hadn't shown interest in tourism to that point really.
I did use a couple of musicians to experiment with them but didn't actually need them as again the gate was getting 2 tier three tenants rather than gaining influencial and overall i feel in the current state muscians are almost pointless as you get too few of them to matter for tourism from great works as they come so late to the tourism game (although not late to the game itself) and it is so easy to gain influencial you don't need to use them on tours where as before they were often the method to push the final mile.
Straight tourism seems to have been heavily buffed with both the changes to the way the additioanl cities debuff works and the addition of a lot of extra sources of tourism from buildings yet culture has not been equally buffed so the only defense against a tourism victory is conquest.
The adjusted tourism column never adds up, using made up number rather than a actual example as not in game atm i would have 1000 tourism and have a net 50% buff with a civ yet could be providing 2000 adjust tourism or 1250 adjusted tourism. This is probably most useful to see adjusted tourism against me so i know how much culture i need to pump out to defend against it and i am sure it used to be accurate but now seems to be almost made up it is so none logical.