The issue is not really in changing monsters or enemies as such, as of course it’s a game and they will have to balance things. The problem is that every fight is a challenge for the party that can potentially kill them if they don’t do well. I.e. every fight is a CR3 at the bare minimum if not a CR5 when you’re at a level 3 area.
Changing stats and attributes is fine but they need to decide if they want to go divinity and make us long rest after every fight or if this is actually a DnD game and balance accordingly. They need to set a target I.e. we want the player to long rest every 3-5 fights or so and stick to it.
If every fight depletes the player or forces them to use all of their resources then this is not balanced like DnD.
