I came to a similar conclusion in about August time. I now believe BIP300 sidechains are our best bet for maximising the user experience for self custody. i.e. low fees, better privacy, and easy onboarding, no liquidity constraints like with lightning. 

Maybe it won’t catch on, but I think Rootstock, RGB, FediMint and Liquid will  have the similar problems as it will lead to federated custodians. 

Ark may be better than sidechains but honestly I dont understand it works technically.