There are a lot of great specific suggestions here. Rather than add any more individual items, I'll just suggest the value of depth, breadth, repetition, and patience. First of all, regarding depth, let's say you find that you really like Dvorak's 9th Symphony, the New World. Well then, dive into more Dvorak. You could try his Slavonic Dances, his Cello Concerto, his later String Quartets, his Symphonies 7 & 8, his piano quartets, and quintets, the Dumky Trio, and more. Or listen to more romantic symphonies of about that period. This would be depth. Or let's say you like one of Beethoven's symphonies or piano sonatas. Well, try listening to more Beethoven. There's a lot of great stuff. If Beethoven continues to draw you in, keep going. If you find a composer you like, go deeper into that composer. Or in terms of genre, if you like piano music, or ballet, or opera, or violin concertos, go deeper into that genre.
Breadth would involve continuing to explore, moving on from something you like to something related but a little different. Try a new composer or explore a new genre that's adjacent to something you already like. Maybe you haven't clicked with opera, but you like Mozart's symphonies and concertos. Then maybe segue into Mozart's operas and from there, into other operas. Perhaps slide from Mozart to Puccini to Verdi. I am a big fan of piano music. For a long time, I loved Beethoven, Schubert, Mozart, Chopin, and Bach on the piano. Now, Schumann's symphonies hadn't really grabbed me. He was a bit of a "meh" composer for me. But when I started in on his piano music I quickly decided, "This guy is fantastic!" Schumann's piano works led me back to his symphonies, which I now really like, as well as his songs, chamber music, etcetera. The broader your musical knowledge and interest, the more readily you'll respond when you encounter a new piece or a new composer. Achieving musical breadth often means moving from a composer, instrument, or genre you already like to something adjacent. Over time, you will have covered a very broad range.
Repetition is also important. A great piece of music can bear repeated hearings, and with repetition, that music gets into your bones. Then you're ready to go deeper into that composer, and also to listen to other composers who bear some relation to that composer.
Let me also add the principle of patience. When I first listened to the music of Debussy, for example, I didn't quite get it. I was coming out of a fairly deep exploration of Bach, the Viennese classics (Mozart, Haydn and Beethoven), and the mainstream 19th century romantics. Debussy didn't quite make sense to me when I listened from that particular context. Still, I was open to the possiblity that I might like him later. And lo and behold, as my musical listening grew broader, I found that Debussy's music suddenly came very easily to me, and now he's one of my favorites. Being a pianophile, I confess that I'm particuarly drawn to Debussy's piano music, so I got into his music via a favorite genre. But if one dismisses a composer as "bad" after just a few hearings, it might be harder to overcome what has become a mental barrier. I still haven't really clicked with Bruckner, for example, but I'm open to the possiblity that I might some day change my mind.
So, coming full circle, think about following the principles of depth, breadth, repetition, and patience. If you follow wherever your interests lead, while maintaining an open mind, that can lead to a lifetime of listening pleasure.