I don't think of items as being time or gold sinks. I enjoy getting items. I enjoy questing for them and purchasing them from vendors.
Have you played D:OS2?
I like items, too, I also LOVE to buy items from vendors. Time and again. A few items.
But in D:OS2 it was a chore, not an enjoyable experience.
The issue you describe is really proper to DOS:2 though. Mostly cause items in DOS: 2 were 90% about stat stacking. So you always had to look through all your items to get the correct ones on the correct character and that was it. No choice, nothing to think about. Just stacking the best stat on the right character.
Items in D&D aren't supposed to give you stats to begin with apart from the most powerful ones as far as I'm aware. They will be more about the various effects/ skills they give you.
So there won't be a need for items to " level up with you". Ocasionally you will swap your 1d6 + 1 weapon to 1d6 + 2....or not if the +1 gives you lifesteal or a spell you want and can't get in another way.
You're applying issues of DOS:2 to BG3 thinking they might do the same mistake but in DOS:2 they had to come up with their own system. Here they're taking the one from D&D so this issue won't exist. They might be other ones but well. It kinda answers your question.
