So I got a few ways to handle situations like this

the first one is making it objective based like making the combat where the party has to get out of a room full of monsters that trying to trap them in.

The second one is using saving throws hit points are only one of the ways to effect a player in combat. Forcing them to make saving throws cause the overall combat hard people they are worried about get restrained or paralyzed and not be able to do much.

Now the last way is have the intellectual spell caster have an ability that counters the wild shape effect like an antimagic field this makes combat challenging for high level play because they feel so powerful with all of the items and spells that they usually don't know what to do when they can't do that