If this was on 3DS the average score would be in the 80s.
This was a huge leap for the series.
You're comparing MH4 with MHW.
Imagine a hypothetical MHW on 3DS (exact same game as the PS4 one down to every detail).
These would be the reviews:
"MHW while ambitious, feels limited by being on a small handheld. We want the big screen experience. When will MH break free from the handheld ghetto?"
"Unfortunately even with a dialing wand, my hand cramped up while attempting the tutorial and I had to go to the hospital for an unrelated heart attack. Ah, the joys of being 400 pounds :/"
"This is the probably one of the best Monster Hunter games we have ever played. Almost as good as 3 on the Wii and 2 on the PS2."