As a Colombian I can say that most people declare full income due to fear of being chased by DIAN (colombian IRS) which is probable the most corrupt institution in the country, meaning that if you don't declare your full income they'll shake you down for everything you have, I've personally heard cases of people making innocent mistakes in taxes and getting extorted for millions upon millions by "honest DIAN officers".

The strata system was created to create a form of "equality" where rich people helped poor people via subsidies, however, this has been abused by both sides since the very beginning (poor people using 10 or 20x the normal amounts of water and electricity to "fuck the rich people" and rich people paying to get their houses declared "historical patrimony" to avoid paying subsidies)

In the end, the strata system was created for a different society that we have right now, nowadays almost all buildings are estrato 3 or 4 in areas where estrato 2 was the highest possible.

I have no idea what could replace the strata system (I'm not a political scientist or anything that resembles that) but I do agree that the system is broken and should be replaced by something better.