It depends on how many minutes of music were out on each side. There’s a lot of 45s that sound great and they’re worth a lot in part because of that for example. A lot of mainstream stuff started to get pressed on thin, cheap vinyl and was packed with as many minutes as possible. So yeah, loss of fidelity there and remastered CDs may in fact sound better. I think you’re probably safe until late 70s before that became practice.
There’s no masters of a lot of rare, non-mainstream things, or at least not known masters. And a lot of great music that wasn’t going to be mainstream for a variety of reasons. Think regional funk, blues, punk, psych, etc. You just can’t get a great digital recording in many instances.
100%. If you can find a quality rip of the vinyl I'll take that for convenience (I have ~1000 vinyl records so I have my fill of that magic) but especially something from long ago transferred to CD in the 80's I'm going to be very skeptical of.
Another huge factor that affects the sound is the damned stylus. It's like switching speakers. Each one has its own signature. Then there's the phono preamp/RIAA filter too! I prefer our modern times where only the choice of speakers matters that much. Think of all the permutations of stylus, preamp, and speakers you had to consider in the early HiFi days.
There’s no masters of a lot of rare, non-mainstream things, or at least not known masters. And a lot of great music that wasn’t going to be mainstream for a variety of reasons. Think regional funk, blues, punk, psych, etc. You just can’t get a great digital recording in many instances.