This arguement is massively overplayed imo. I've not heard one supporter say they're fed up of watching Liverpool play Utd twice a season - why would they say it about Liverpool vs Real?
Is Liverpool vs Real/PSG etc in a group stage of the CL any more interesting to the neutral than Liverpool vs Utd in the League? I don't think so.
I didn't say it was a big issue nor that people would be 'fed up' - but they might be less interested. I'm not 'fed up' of watching Liverpool vs Utd but I don't go out of my way to watch it, why would I? It's just another match and it'll probably play out the same way it played out the last 2 or 3 times it was played in the previous 12 months.
Liverpool vs Real though, even if it's a group stage with less weight on the actual result
is more interesting I think, yes - they're not teams that know each other inside out playing out the same tactical battles - it's a potentially completely new clash of styles, full of unknowns, players that they haven't learnt to play against, a different challenge for everyone involved. It's all amplified a bit from a normal game because the very fact it's not a normal game throws in far more unknowns and makes the entire thing more interesting to watch unfold. Similarly, I may well have interest in watching Real play Bayern, even though I have no investment in either team, as the fact it's a one off can throw up more interest but I don't really care about watching Bayern vs Dortmund for the 3rd or 4th time this season, last season or next season.
We naturally like to create 'special events' too - we wouldn't celebrate Christmas monthly because it'd completely dull how special it is, but who wouldn't want to exchange presents, decorate the house etc. monthly? It's a good thing, so doing it the same over and over, more and more must be better?
It's by no means a massive factor but I don't think it's not a factor at all.