There are people that do not pay taxes, but they are compensated by those who pay. The net effect is actually that the tax burden vs GDP in Italy is higher than in places like, say, Germany.
The reason Italy has a high public debt is not tax evasion, is excessive public spending. The reason many business are failing is not tax evasion, is a crazy tax law that kills many to reward few. That is why many Italian hate taxes, because they are unjust.
that's reasonable analysis, and my initila argument was deliberately simplisitc just to make a point, rather than to complexify Italian taxation systems. You and your interlocutors among you seem to have covered this nicely for anyone who was interested in the details (which I didn't have time for).
Do inform yourself a bit on the topic. It's way more complex than you think.