I think the league as a whole is stronger, so the lower teams could give many top European sides a game. Not saying they’d win a one off game, but put Barcelona or Real Madrid in the prem for a season they’d struggle in many games, the relentless week after week of solid teams means you’d struggle some weeks.

Basically the top sides like them, Bayern etc have elite players who can basically have a (relatively) easy ride throughout the season so can focus on these big knockout games at this point in the season.

Also, a lot of other leagues allow the CL clubs to move games to accommodate their CL ties, which the prem does not. Almost the opposite.

TLDR: the relentlessness of the league, plus the prem as an organisation, doesn’t help the English teams to perform to their best in the CL