There just is no industrial revolution in the game.
My feelings exactly.
Industrial revolution fell seriously ill in CivV, and now, in Civ VI, it is comatose, as good as dead.
factory bonus, cost
civ4 +25% 250
and +25% if the city has any powerplant, which brings it to cumulative +50% as in previous versions
To be honest, there was. In the beginning, all factories stacked, which was an "industrial revolution". However, since people started to build many small cities close together, to get maximum numbers of factories, they removed that & had only one factory (except when you use Magnus). So, basically, in the beginning it was too strong & now it is too weak.
i didn't like stacking factories. ics ruins the game.
Stacking, at least, was more fun than no stacking, as it did give some impression of a "revolution". Maybe it was not the best implementation, but just removing it completely was even worse, in my opinion. Now there are all sorts of production sources, which have little to do with being an industrialized nation.
Factories should also provide more slots and a much higher ouput per citizen. The +2 per citizen is the same as for a workshop and it provides only +1 slot.
Oh, yes, specialist citizens are so insignificant, there's very little incentive to use them. I'd like to see them gaining much more importance.
And coming back to factory effect stacking, its removal quite saddened me as a very clumsy and hasty "nuke it all" decision. Instead the developers could leave it be or at least halve the spillover effect (1,5 cogs to other cities in the radius) and take their time to bring variety. We see more alternative building options appear in various districts, why not to make this with factories?
For example, there could be a number of possible and mutually exclusive factories: creameries for cities with cattle in their radius, textile mills for those who have sheep, steel mills, if the city has coal and iron resource in its range, furniture factories for cities with lumber-mills, canneries, for cities with sea resources, jeweller shops (gold, silver, diamonds), electronic factories (copper, also, sorry Japan, you'd have something else), aero-space complex (aluminium) and so on. The area effect of the same sort of factories would not stack or stacking would be limited, but the effect of different kinds of factories would add up.
Besides, the yields could be different, split between food-production-gold-and perhaps amenities elements, depending on the base resource and it's quantity worked by the city, maybe there could be alternative factory types for the same resource, for example, in a cattle rich city you could build either a creamery for more food, or a tannery, for more production. There could also be yield bonuses not only for the number of a particular resource in the city radius, but for their adjacency to the IZ - for more thinking about their placement - what do you want - better yields or more covered cities?
Making production buildings much more reliant on bonus resources, such as forests, fish, copper, etc. would also be a great help in reining in unrestricted chopping, which is now the name of the game, especially with Magnus, and is completely out of control.
There could also be more types of powerplants, bringing back coal plants, if you have coal, hyrdoplants, if IZ is on a river, nuclear plants, if you have uranium and coming with a small probability of a meltdown, of course

, solar plants in deserts.
And, of course, railroads. That could be a tile improvement, buildable for charges by builders, increasing movement (modern roads movement could have a bit of a nerf) and having an effect somewhere along the lines of a permanent internal trade route, boosting production, food and gold in connected cities, also giving more cogs for connection of the IZ to the relevant resources and IZ to the city centre.
This could give a lot more production, so the production cost of later era units and higher tier buildings could be corrected to take account for it, if necessary.