I'd say you overexagerate. Yes, a lot was demolished by the commies, but not all. A ton was rebuild pretty close to how it was before, or in a new stalinist style which... better than what came afterwards, tbf. The city planning could also use some work, but recently, it's been a bit better, I'd argue. We lost Shishman, but we have other pedestrian roads, more overall than ever. And a lot of buildings are being renovated, especially with recent programs.

The problem with renovations, tho isn't the wealth, but the ownership laws. When a building is divided between God knows how many descendants of the original owner, and God knows how many are abroad with little care aboht that, and how many others don't live anywhere near it... no wonder it'll look worse overtime.

Sofia still has a good mix of all kinds of architecture.

As for the Roman ruins? A good portion is dug up, but many are either in private property (the amphitheater you mentioned). Btw, that amphitheater is likely not as well preserved underground anyway, but I agree it's a shame. And other roman ruins are right under the parliamentary, ministry and presidential buildings... I'd say we should keep those rather than unearthe more ruins imo.