Please specify what you mean by "decentralization". If you want I can explain the classic (fallacious) bitcoin core argument here, which is in essence: some poor person in the 3rd world needs to be able to fit the whole blockchain on their raspberry pi.
EDIT: Meeting ended early, so I'll just take this on now. First things first:
> Sure, doubling the block size a few times would likely be fine, so Bitcoin may be overly conservative right now, but I firmly believe any long term solution will require some form of “layer 2” for payments.
So, just to point out the absurdity here explicitly, you are worried that Bitcoin's "decentralization" will be harmed by block size increases eventually, to which your solution is to force a layer 2 payment solution which essentially will force transactions to route through centralized middlemen, rather than the transaction publishing to the blockchain, which is literally the thing that gives bitcoin its value. You don't see something weird about that reasoning?
Additionally, the "you can do a few doublings but eventually you run out of space" is a misunderstanding of how exponential growth works. The capacity to store data has increased exponentially over time, there's no reason to think it won't continue down that path. (I'd really like to avoid going down the "moore's law will end" rabbithole if we can)
Oh, and for good measure this goes into the Bitcoin Core dogma that what keeps the Bitcoin network secure/decentralized is the number of "full nodes" (nodes that have a full copy of the blockchain but do NOT mine), whereas the real security of the network comes from the miners, and it is the capitalist market mechanism of competition for hashpower that gives Bitcoin its resilience to double-spends.
Finally, the whole justification for the hurt "decentralization" is as I said above: the argument that everyone needs to be able to have their own copy of the blockchain. Firstly this ignores that most users use thin wallets and have no need of the whole blockchain; this does insert some trust at a point in the chain but it is a tradeoff most users are more than happy to make for their use-cases. That being said, like I said above, there's no reason to think that one can't keep a whole copy of the blockchain. Indeed the Bitcoin Core argument is just that it's prohibitively expensive, not even that it's impossible, although they define prohibitively expensive from the arbitrary threshold of a random 3rd world person living in poverty.
It's doubly ironic because the literal result of refusing to increase the blocksize - which, not that it matters but Satoshi was never against a blocksize increase; indeed he assumed it would happen - is skyrocketing transaction fees, so that same third world person Bitcoin Core pretends to be so concerned about now has to pay $80 to buy their $1 worth of rice. Oops.
Now the argument comes in: "no they don't need to pay $80, because they'll use the lightning network and thus never need to push to the blockchain!" Which I already addressed above but just to recap, now you've introduced a system of centralized middlemen, AND the very design of the lightning network means that (a) you have to make at least one transaction to seed your "store credit" (and even a single $80 transaction is unaffordable for our hypothetical third world person), and (b) they are required to pay in advance which again puts unrealistic financial stress on them. (For those who aren't familiar with the lightning network, the idea is basically that rather than making bitcoin transactions like normal, I send $20 to a middleman who now gives me $20 of credit and now I can "send" money via an elaborate form of IOUs that never end up on the blockchain, until some point in the future where you resolve onto the chain. It's an optimization strategy that destroys all of the utility of Bitcoin in a misguided attempt to "preserve its decentralization".) If I'm failing to be articulate here it's because the whole concept is so mindblowingly absurd that I don't even know how to properly explain how ridiculous the whole thing is, and is a large part of why I assume that anyone who advocates for it has just literally never used Bitcoin except to speculate