Certainly, one missed call or VAR flip can determine a two-legged knockout tie. But Liverpool had to get through: PSG (group), Bayern, Porto (not worldbeaters, but Primeira runners up), and Barcelona. IMO, Tottenham was the weakest side they played in the knockouts, particularly since Kane wasn't 100%.
PSG, Bayern and Barcelona are all better than anything outside the current top two in the PL. Getting past them takes fewer matches, but they're better teams. There's a reason why England is still #2 in current coefficients - they're top heavy just like all leagues and just a bit more so than Spain.
I don't think the PL, in general, is a 'tougher' competition. I just think it's set up poorly and it discourages parity. They start too early and they play too many matches over that December-January stretch. They have two domestic cup competitions. It's more a test of quality depth than anything else.
It just seems that overtaking City is near impossible right now. Liverpool will likely improve next year. But I don’t see them amassing mid 90s in points. Nor anyone else.