If you use Buffout 4, locate in your crash log "Probable call stack", if you got something about KERNEL32.DLL and NTDLL.DLL.
This guide should fix a lot of crashes, i have a lot, a LOT of mods and it doesn't seems too crash anymore, i do expect to crash but fortunately not as much, it will be because of compatibility problems caused by different mods.

What you need to do is simple, you have to open CMD as an administrator then type “sfc /scannow” and hit enter.
Once it is done, try out your game, if you were having crashes because of such DLL, it'll fix it for sure, now it doesn't mean that you won't have crashes anymore as there are other crashes caused by different reasons.
But as i said so far my game is not crashing anymore while it was crashing barely 3 minutes after play, or even by fast travelling or getting inside / outside.

For the other crashes, make sure to check compatibility issues with FO4Edit and correct them.
Never delete mods mid-game.
Never change an esm / esp to esl mid-game.
Do not eslify everything.
Merge mods properly if you're goung to merge mods.
You can use old mods but some such as AWKCR are badly made and they should not be used, there are guides online.
Not sure about ragdoll mods, i know they are bad for either Fallout: New Vegas, Fallout 4 or Skyrim (Special Edition), not sure which game it is bad to use such mods.
Do not use more than what your computer can handle.
Watch out for corruped files (meshes, textures, etc).
Watch our for bad configs (ugridstoload too high for example).
And the list goes on.