It's to do with the atmosphere that the Liverpool fans create. What I am saying is that Liverpool, even at their best, were pushed by their fans a lot. The fact that this season they have fallen so far in all competitions, specially at home, has much to do with their empty stadium. No other big team has fallen so spectacularly since the lockdown.
Not that i think Liverpool would have been able to eliminiate Real with fans, but i agree that liverpool or english teams in general are very dependent on the fans and atmosphere which in many cases helps them overcome their technical short comings against south european and specially spanish opponents. Without fans that extra push and adrenalin is missing and as a result teams like liverpool find themselves on the losing end of matches against overall better footballers of likes of Real.
To me it doesn't make sense, I think they are just not playing good soccer and have become predictable, Injury has also had a good effect on Liverpool.
The reason I say is the due to following facts:
[1] The same Liverpool team played great football half a season last year in empty stadiums and in fact they played well even 1/2 of this season
[2] Liverpool is doing very well in away games and not at home
[3] There are multiple English teams in semfinal of Champions League and Europa league.
[4] Majority of players of the top teams are not English
I mean if you argue a mid tier English team doesn't perform I would understand but not in this case. At this stage, Liverpool even can't beat mid-tier teams consistently and they are doing much better away than home, so again "Team is not performing, bring some juice to the team coach"