You might hate some of my answers (because I have asked similar questions to yours over the years)
but some of this may work for you, in which case it’s an easy fix.
If you’re working in 24- or 32-bit (or whatever Cubase is up to now) and then rendering out your song to a
lower bit rate, make sure in the ‘export mixdown’ window you have DITHER turned ON.
If you were working with all 24- or 32-bit, and you export to a lower bit rate without Dithering, it might
sound like crap no matter what software you’re using, that’s just how it is.
Cubase loves bass, meaning: Cubase will retain each track’s FAT bottom end if you don’t EQ it out. So Shelf out
all bottom end from all tracks that aren’t bass instruments.
Use a good mastering effects chain on your master channel, or don’t use ANY AT ALL.
I export mixdowns without mastering effects and usually find that Cubase sounds extremely good.
Somebody ^up there^ in this thread said something like “refine your mixing skills”. Do that.
Do you know your human ears actually get fatigued very quickly? If you work on a song for an hour, you are listening more intently than you listen to probably anything else, and no matter who you are or what your age is, your ears WILL get “padded” to certain freqs and your perception of the volumes of individual instruments will get fouled up. So…
A. When you’re blending your tracks, put the master fader very LOW (-12 or even less). You can even lower every instruments channel down as well.
I’ve always said (18 years of using Cubase) "I keep trying other DAW’s and I swear that Cubase makes anything sound good. That includes its tolerance of cranking things up too loud and still sounding good.
Lower each track down, lower your master fader when you mix.
Mix it…raise up the master a little bit…mix it more…raise it up more…repeat.
BEWARE MASTERING WHEN YOU HAVE REVERB on everything. If you like mud, render audio files with reverb on them, then put mastering effects on your mix, you will get your mud.
example: a vocal track. you might put reverb on the vocals so they sound big, then later on compress that track, and then compress the mix, and it’ll sound bad. get levels correct before putting REVERB on anything.
I don’t know, I just realized I could go on forever with all this and I’ve been doing it for a pretty long time and I have posted some flaming horrors in the Cubase forum (which is gone now) over the years.
I’ve heard it accurately described like this: “Your first 5 songs will sound like garbage”.
Mixing (unlike composition) does have “rights and wrongs”, which is actually why I prefer writing and hate mixing.
Realize that Cubase is a professional DAW that looks and feels like a big beautiful toy so it’s easy to get tempted by it all and go creatively wacky (which is a great thing), unless you’re in the Mixing phase of your song, in which case you want to do certain things correctly rather than outlandishly.
Hit YouTube, buy books, and get some pointers.