And just because the AP + MR item would be gone does not mean another can not be created.
Making GA and Banshee's which were both defensive items commonly picked up by anyone to deal with an enemy threat attached to AD and AP is one of the biggest problems the game has compared how it use to be.
In patch 7.9 GA and BV were both changed from being reactionary full defensive items to GA having AD, armor and the revive passive and BV having AP, MR, CDR and a spell shield that recharges ater 45 seconds.
Enemy Leblanc blowing you up? Build a Banshe's and get some MR and a shield to block her first spell You will have a much better chance of surviving.
Malphite building Full AP and one shooting you with zero chance of counterplay due to his ult being unstopable? Build a Banshee's veil.
We need counter building back in the game. That is likely the single biggest thing the game has lost that is a truly negative impact.
It wasn't like BV was OP outside of a few patches in I think it was season 3 where you would literally see 10 of them in an hour long Athene's restoring mana faster than you can use it game but it was a necessary form of counterplay that made some champs fall off at some point instead of being a constant threat you could do nothing about outside of hope your team could peel.
The thing is that trying to pop the enemy squishies banshee's makes jsut going in and one shotting them require some actual planning.
Yes this will require marksmen to go back to building a purely defensive item if they see an enemy as a threat they can otherwise not contend with. And in turn it will counteract damage creep to some degree but not all the way due to keystones also adding to it.