It's the old "Garbage In, Garbage Out" ...
If it's a poor recording and/or a poor pressing it's never going to sound good!
Saying that, I occasionally have a singles night (!) where I flop out my 7 inchers from the late 70s/early 80s, and while not having the absolute fidelity of something like Al McDowell's Time Peace, or Nazaire's"Who's blues?", they don't sound bad at all, especially things like The Monochrome Set's "He's Frank" or DAF's "Kebabtraume"...
They, however, have the immortal words scratched into the end groove - "a Porky Prime Cut". Always wanted to have a record of my own mastered by Porky!