I also agree that Monero has held it's own as far as a store of value, but I don't hold any XMR for extended periods of time. I can't think of a single other alt that even comes close to bitcoin's superiority in that regard. With Segwit and now Taproot making transactions smaller and lighter, I tend to think that even Lighting's days are numbered.
I can't agree with the last statement. I'm the first to point out that Bitcoin on-chain transactions aren't 'too expensive' and that we need 'this new hot coin' to fix it etc., since I'm very happy to pay a few cents to a dollar for a transaction. However, these fees will never come close to Lightning fees. Lightning is cheaper and maybe more importantly, the fees don't really fluctuate like on-chain fees. You could e.g. use Lightning when the mempool is full and do on-chain when you can get transactions confirmed for 1sat/vB. What's unique compared to using an altcoin is obviously that you never 'leave' the Bitcoin currency so there are no conversion rates to worry about and no exchanges needed either. Except for maybe an 'instant exchanger' that uses submarine swap technology like bolz.exchange.
Something Hal Finney wrote once does keep popping up in my mind, however. Once he suggested that eventually each "bank" would create it's own stable coin that runs on a chain with fast confirmations, and it would all be backed by hodling bitcoin. If Binance and Coinbase weren't so anti-bitcoin I could almost see BNB or USDC fitting the bill.
What's interesting about older statements from the early Bitcoin community is that they often do manifest themselves in the future, but a bit differently than what the original wording suggested. Similar to how sci-fi books and movies predict(ed) the future.
In this case, I'm with you that 'banks' will not be the traditional banks themselves, but similar entities. Exchanges could have filled that spot, but so far they all look pretty bad and anti-Bitcoin; mostly shitcoin-focused, with the purpose of maximizing their own profits. It's possible that larger Lightning nodes or sidechains will take this role.