[zork]

It really depends on your intentions.

I write addons for myself in first place. I need to be interested in them and it is my free time going into that.
Since my intention is personal I get satified by just writing stuff and bringing ideas to life.

It can feel rewarding if many people download your stuff too but I think it should be driven by your self motivation in first place.

Regarding advertising...post some screenshots of your UI or addons on MMO or Reddit. If people like what they see they might use it.
Not sure if it really got me sth but I have links in my sig to my UI.

Addionally don't be to disappointed if the downloads are low. WoW subscriber rate is dwindeling and most people have settled on their addons.

Patches can make room many new addons since there is new API stuff.