It’s not just specifically the records he (occasionally) releases that makes him relevant, but rather how he approaches making art and music. He got the jump on many modern music-making techniques that we take for granted, for sure, but his most important contribution continues to be the way he encourages musicians to think about how they might approach art and music. These things are always relevant.
An interesting (and accurate, I’d reckon) quote from a 2014 New Yorker article:
his catalogue of recordings doesn’t completely contain his contribution to the pop canon. When someone lies on the studio floor and sings at a microphone five feet away, Eno is in the air. When a band records three hours of improvisation and then loops a four-second excerpt of the audiotape and scraps the rest, Eno has a hand on the razor blade. When everybody except for the engineer is told to go home, Eno remains.
While his most significant releases were from the 1970s, my own favorite Eno record is The Drums Between the Bells, released in 2011. As it happens, one of other my favorite Eno release isn’t an album, but rather a book… a journal to be exact, called A Year With Swollen Appendices. Also, there is a wonderful book about Eno’s work called Eno and the Vertical Colour of Sound that is well worth a read or two.