I owe you the apology - because “lagging” YouTube issues are recurring for Desktop users, and I was moving too fast, failed to notice the “iOS”.
YouTube adblock issues are a running battle - back and forth - and there are a mixed bag of sometimes sturdy vs sometimes temporary “fixes.”
I use the Private Browser Only mode, and that, I suspect, helps with visiting YouTube (I do not have any Google eco-system accounts).
I use Brave Browser (iOS) v1.78.1 (104) and a VPN connection. Sometimes the “fix” is, for me to change the VPN server (disconnect . . . wait . . . reconnect). Sometimes the fix is clearing cache, etc. Sometimes a complete quit of the BB app, and a forced shutdown of the iPhone.
Re moving too fast, lately - and I forget what happened - I had to completely remove BB and its data/settings; then do a fresh install. My how to: