Producers usually start with a kick, snare/clap and bassline. Working the other way around can be difficult.
I always start with a chord progression. Then I pick proper kick, snare, bass that fits to that chord feeling. Since I never know what kind of feel chord will have, I can't pick drums or bass.
Making winter type of feel chord progression can't have summer type of drums or bass if you catch my drift.
Seriously..there's a little more to it that just adding reverb. For a start, you don't know what other people's tracks are going to sound like, and adding reverb just might totally fuck up their work..just saying.
Mastering requires at the very least, some attention to the work being mastered..and while such automated services may work for some kinds of music, at this time they don't work so well on other kinds.
Personally, I would much rather have a human set of ears actually listening to my work while it's being mastered..again, just saying.
Please don't listen to me or what i just typed. It can be true for me and not so true for you. Trust me. This advices(attachment;pic;img;infographics) about mastering can work but only in certain conditions.