Large MP3 Library from 2000s CD conversion/rip/sunset

i wouldn't bother streaming high res is going to sound better

MP3's: in the trash,

really, they are so compressed, they are from the days of "I've got more songs than you do". 

Yes, but not one worth listening to.

You could use them to learn a bit about various artists and then listen to higher quality versions, but you can do that online, Pandora ,,,

It really depends on the quality of the rips. There are different types of MP3 ranging from 48kbps and 96kbps (which are only tolerable for audiobooks, and even then just barely), to 320kbps which is actually quite enjoyable for music. Not lossless quality mind you, but still very listenable. 

For the higher quality rips, MP3 is sort of like Spotify was for many years, prior to the recent lossless update. That means perfectly adequate for music exploration or background listening, if somewhat lacking for dedicated high quality playback. 

Having said that, chances are a modern streaming service like Tidal, Qobuz, or Apple Music will have the majority of that music in lossless form. With those at your fingertips for very reasonable monthly pricing, I'm not sure how much use I would have for the MP3 collection. Even so, definitely don't throw them out. Storage is cheap enough these days and there may be some rare gems that you can't easily find anywhere else.

I have a HD filled with iTunes from back in the day.  I plugged it into the usb input of my Cambridge Audio streamer and the files all appeared in a separate library in the streamer app and played