There’s nothing arbitrary about it. Yes, it’s possible to make a larger op return and put it into a block, but it’s not trivial and if you check the number of larger than 80 bytes op returns, it’s only 0.01% of all the op returns since 2014. So the limit works as intended and now it’s nuked out of the water to make it easy for some VC pressure groups that want to turn Bitcoin into a crappier Ethereum.