"close to mozart and beethoven" is kind of a (forgive the term) problematic premise.
there's not much actually stylistically close to Beeth/Moz right now (outside of film scores) because we are living in a very different time/society/economy/political landscape etc.
if you just want something similar to beeth/moz in terms of complexity, there's lots of "complex" music, very complicated, and there's lots of music that sounds "epic" or "classical" (again, film scores), but i'd suggest the following for you:
Einojuhani Rautavaara - finnish composer, beautiful, lush, neo-romantic (meaning reaching backwards to late beethoven/wagner/liszt/strauss etc)
youtube.com/watch?v=po3gXcMd31M
Also check out his symphonies, especially the later ones (they get more "listenable" as he gets older)
Arvo Part - estonian composer, still alive. Beautiful music, simple, monastic, approachable:
youtube.com/watch?v=FkHEjiuYBuM
one of his more complex works:
youtube.com/watch?v=2DJUN2M3D-E
Joep Franssens - dutch i think. eventually he decided upon a return to early palestrina vocal styles for much of his compositions. this one will blow your nuts off if you sit and give it the hour of attention:
youtube.com/watch?v=wLkmMEEiNBk
Also check out some post rock bands like godspeed, william basinsky, sigur ros.
HAHAHA oh and this youtube chanel that cracks me up beause it lists minimalist music in terms of its "level" of minimalism or difficulty in listening...
youtube.com/channel/UChR3WgVe-1My-OUYtHngXdw