I think you can design in error tolerance, with a bit of imagination. Imagine a flotilla of connected balloons, instead of one giant balloon; build in enough tolerance that a sagging balloon is supported by its neighbors until it can be fixed up.

Ultimately, it's a question of building a floating thing, and keeping it floating. This strikes me as not-too-hard, compared to the usual space problem of trying to hold oxygen in a bubble in a vacuum. You just need a sustainable way to 'recharge' the balloons; that really just means filtering lighter gasses from the air and pumping them in faster than they leak out. The Venus atmosphere is primarily CO2 with a bit of nitrogen; the game is then filtering out CO2 and filling the balloons with nitrogen. Coincidentally, we have people putting lots of thought into efficiently filtering CO2 from air already...

Does it need to float? Could not some sort of mountain plateau work that's the right altitude but perfectly solid ground, just high in the sky?

The safe height is on the order of 50 to 60 kilometers up, so that’s a tall order.

Maybe the expectations of a "cloud city" should also be lowered. I guess it would be more like the ISS and less like Lando's station.

The general idea of colonization of other planets is in general much farther away than your average tech billionaire wants us to think :)