Many rock recordings of that era are quite poor - others are quite good. But yea, lots suck. Many many reasons, one famous one being that several of them were going deaf with traditional old male hearing loss, accelerated by their jobs. Pete Towshend was afamous for over-riding on mixing -- balancing what HE heard.
Many are also heavily compressed, and the house sound was achived with mix after mix, so you have a 27th generation tape in effect. Not exactly audiophile purity.
On the other hand, listen to LA Woman, or much Bowie - surprisingly good.
I've noted many times that a huge advantage of streaming digital is that you have access to remastered copies of great old, rock and pop albums. Wile they are not perfect they are all much better - and often that trumps any quibbles you may have with digital. Certainly it does for me - big time. And i have some VERY good vinyl gear.
The best recordings remain purist. 3 mics and no mixing to speak of. Verve, some lue note, mercury LP etc. Those are the polar opposite of most rock mixing and production techniques. After all, George Martin was the 5th Beatle.
G