Me, after an accident on my mountain bike saddle:

According to Endgame, the stones need to exist for the universe to function - so no, the stones cannot be 'destroyed' otherwise the entire universe ends. If the stones exist in any form, they can be repaired - especially if they were 'reduced to atoms' because we have at least seven characters in the MCU capable of doing so.

That's not to even mention the fact we have a working time machine in the MCU and any future problems in the MCU could easily be fixed by the time machine they still have - and have zero reason not to use because it has zero consequences for them.

The MCU as a narrative completely collapses with Endgame - no more emotional stakes, no more consequences, no more justification for any bad things to happen. It simply has too many contradictory aspects that would enable the heroes to automatically undone everything that happened.

As far as I can tell the only way to fix this utter disaster is to claim 'The universe is collapsing slowly' and have Doctor Strange realize this in 'Multiverse of Madness' where we see some of the alternate verses start to collapse. Then when we get the next Avengers movie we have them fighting to defend against a wave of energy that is wiping out the universes and ends up stranding a few in the same universe (e.g. Fantastic Four, X-Men, Blade, etc...)