its got nothing to do with mempool size..
even if mempool was 500mb but only had 150mb of transactions in there. pools can still deny adding transactions below a threshold. leaving people waiting and needing to RBF to reach whatever threshold mining pools want
so in a 4decades in future scenario when mining pools are going to demand fee's they can just leave the cheap fee tx in mempool to fester for 2 weeks, causing people to RBF upbid their fees to get recognised
I'm not talking about denying . Currently mempool is filled so miners do have to choose , even if they wanted to pass all transactions they can't . This is a condition which can happen with any mempool size . Even with 1 MB miners can deny to add transactions to blocks even if there are higher fees than what would be normal . In fact , it's on their best interest to mine empty blocks as long as subsidy exist . By best interest i mean their chances of finding a block is probably higher with an empty template .
So , without the option of denying , how would a mempool and blocksize increase would affect transaction fees ?
as for leaping to "visa levels"
that debate replaces "scaling" by suggesting the only option is "gigabyte blocks by midnight" to then argue that the network is not ready to even do that. to hope it ends the debate about any type of scaling.. and yea idiots been playing that bait trick for years
the actual scaling is not just "jump blocksize to XX"
its more nuanced
a. punish the frequent spammers: if it costs only them excess fee, they transact less. meaning more genuine people can take the space
b. leaner transactions: punish or prevent bloated transactions, meaning more genuine people can take the space
c. remove the blocksize miscount of 4mb (1mb base+3mb witness) cludge. so that any and all transactions get full utility of the full 4mb space
d. SCALE the blocksize in incremental amounts over time.. no sudden leaps to stupid amounts
So , let's consider a real bussines . If you had a store with a range of customers would you punish the ones that prefer to buy from your store ? And you would try to reward the ones that buy from you occassionaly ?
And what genuine people means ? There are people waiting with their money in hand to have their transactions get into a block . What makes your transaction more genuine than someone else's ?
As for the incremental scaling . There's been 13 years since the launch . 6 years since blocksize wars . I remember Adam Back , Lopp and others saying at that time it was ok to increase it . Right now , according to what most devs believed , blocksize should be at least 32 MB . How big do you think blocksize should be currently ?