The cost of life is low for anyone working in IT, especially remotely. However, I wonder if the infrastructure makes it worthwhile. The roads in Sofia have probably not been repaired since 90s. And there's no public transportation routes available in Google Maps.
With respect to taxation, I wouldn't say it is easy to avoid. It surely is for those that are close to the governing class, but not for the average Joe/Company. Quite the contrary. If you consider doing business in Bulgaria, I would advice against keeping your capital and intellectual property in a Bulgarian corporation. Everything that makes > EUR ~1M revenue/year shows up on the radar and then you either have to play on their rules (e.g. sponsor a political party, give them a share of your company at their terms) or you will be chased down by the huge government repressive apparatus (tax authorities etc).
I don't think this signifies anything though. It's up to the cities to decide if they want to publish the routes and timetables, and many choose not to. Including western cities, such as Montpellier and others in France.
Being part of the EU it’s easy to find an IT job, with all the work from home initiatives now more than ever. SO being the poorest country in EU you can get to some ridiculous standards of living if you are in IT.
And in the recent five years or so the bigger cities in the country have upped their game quite a bit. Before the covid crisis I liked to hang out with foreigners visiting the country and all of them mentioned it being a very positive experience. They often start researching rent prices and such.