This is one of those situations where Table Top doesn't translate perfectly into a Videogame.

"Set ability to X" items are more powerful/build-defining in Single Player Games with no loot randomization because you can meta-game it much more easily. The other issue is due to a design choice by Larian. With no item attunement system in place, the game will revolve more around magic items because they can contribute so much more to a character's power.

It probably won't break the game for most normal players, but we'll probably see a lot of min-maxers or speedrunners dump certain stats and rely on these items instead. This existed in BG2 also (ring of human influence, STR belts), and I don't think it was too disruptive, but it does force optimization towards certain metas.