The important thing to remember with Starship is that the last two flights incorporated an entirely new design.with multiple experiments. These were fundamentally new rockets largely unlike their largely successful prior versions. Rather than a tweak of a nearly successful version to fix a few things we saw major changes one or two of which unfortunately is causing some catastrophic problems. They never got this far, but even just the tile system included probably a hundred different experiments.
Unfortunately since they didn't get that far it is also possible some of those tile experiments will cause catastrophic failure on re-entry if they try them all again. The thing about experiments is you need to to survive long enough to get to them. Hopefully some of those experiments were more about manufacturing rather than survivability so they can down select the most promising alternatives next ship in production. Regardless, we are still seeing a lot of changes each flight and those changes have the potential to not work.