It's not hard to maje content for higher level parties. The rules ate there. Yeah the mage can spam hold person bur why? Many enemies will save
Wish can be cast 1ce per day in 5e. Why would you normally waste it on casting a weaker spell? There's also limits to.its power. BG2/TOB, HOTU and others have liven making content for high level/epic characters is extremely doable.
Not getting to try out higher abilities and spells would be sad. Afterall, that's one of the coolest things about leveling up - finally getting access to high power goodies.
