The fact that you're using real instrumentation is awesome. The structure and the composition itself is nice in terms of progression.
I know one thing I do since I play a lot of real instruments is improvise a lot and then record over the improvisation. Improvisation is the way to practice composing with repetition, where you have this constant feedback of what sounds good and what doesn't.
The clustering of the chords starts to clash. The more bass-oriented the instrument, the fewer notes you want close together, it makes it muddy.
Mix wise, it definitely could use reverb and spacing, especially with all of the bass. I'd say the tone of it to me felt somber and heavy.
The fact that you have those instruments and can play them is a huge asset. I really *really* want to hear you loosen up with your instrument and make some stuff in a more loose fashion to develop that more instantaneous musical intuition.
The vibe you set here is really cool, so I'm definitely excited to hear more.
Edit: the cello has such a big range that I would use that as its core strength, and really continue to improvise on the instrument.