Drainage systems have improved significantly plus the sunlight racks.Premier pitches are now mixed with a small % of artificial grass, this helps a lot, to keep them in great condition.
In the 70s I remember watching Liverpool in various european midweek ties. It always was misty and the Anfield pitch resembled a turnip field.
Not sure it's to do with playing reserve games elsewhere. I was at Newport on Friday night and the pitch was immaculate. A fourth division pitch and they play rygbi on it.Playing reserve games away from their main ground for most teams has improved pitches massively, plus those mobile sun racks they use to keep it in tip top condition...
I was watching the Boro Roma home game the other day on YouTube and the pitch looked like a swimming pool... I didn't remember it being that bad.