To play a devils advocate with some of the arguments:
  • Monero could have more layers too, it has some "smart contract" capabilities and it's adding more (see the developments around BTC-XMR atomic swaps)
  • The fact that TCP/IP (and related protocols) aren't encrypted is also the reason why it's so easy for a country to block twitter.com or facebook.com for all of its citizens.
But I agree with your underlying point. If the current BTC blockchain would be twice as big as it is currently, I would probably not be running a node (because 2TB SSD was a bit too expensive to my taste compared to 1TB).
The one perspective that I'm interested in is whether Monero is actually the privacy layer on top of Bitcoin. If we get bi-directional atomic swaps you could easily imagine having a Bitcoin wallet that has a magical button "clean my coins" and it internally swaps for XMR and back and you get coins without KYC. You don't have to care about anything Monero, you can be fully on Bitcoin standard and yet this can easily provide you with privacy.