hi!! i found this question tough to answer and i kept erasing and rewriting things AHAHA - my honest answer is that it depends on every artist, and what they want to achieve as an artist, and that might not the answer you want to hear. it's a very nuanced topic, and i just am not capable of creating an answer that encompasses all artists' viewpoints.
for example, if you take "success" to mean work/income - a lot of artists who have traditional work in the arts (e.g. animation, illustration, editorial, comics, children's books) may not need to find work online, but maintaining a social media account certainly can help boost. on the other hand, relying on freelance/commissions - unless you already have a steady stream of private clients, artists promote their commission posts on places like twitter and vgen. on the side of merch (artist alleys/online shop), it's not a bad idea to get your products out there and constantly share them.
i think growth nowadays on social media is largely a luck and numbers game. fuck around and find out ya kno?!......... you can be as active as you like, but it's a rough world out there, and "being active" won't 100% guarantee "success"... if you have fun being active online, yapping, making reels to boost growth - i won't stop you!
i think for the sake of most artists similar to me, i do animation work + merch (artist alleys/online shop). animation is not such a hot industry right now for my specialties, so im focusing more on merch in the meantime.
personally, i was more active on socmed when i first started posting digital art. but the landscape of online spaces/fandoms have changed drastically since 2010, and my schedule has too changed since then - finding time to be online is getting harder and harder, and more tiring/less interesting tbh... :'D
at some point, being on socmed too much broke me, around 2019-2021. i realized that i prioritized quantity over quality, i wasn't committing to drawings, and they just looked sloppy and boring, without putting effort into improvement (which is a value that is very important to me). i would constantly worry about why my drawings weren't "successful" (not well received by others, no one had anything to say about some of these drawings). i had to take a step back for my health, and nowadays im not so active because of that. it's ironic how i found my account "growing" the most when i posted less shite online. (to reiterate, this was just my own personal experience).
i'm lucky enough that i think my work is pretty established by now, and i post art maybe... every month - 3 months on average? that may be really slow for some (people usually recommend 1x a week?), and my growth/engagement could be better, but i think i do fine for myself. i do like to talk about my art process here and there, but other than that i don't think i'm super active compared to other artists.
i'm not sure if you wanted tips on widening your reach online, tbh i didn't really do anything special besides preferring to post at night in my timezone, and being very patient (as i don't think i had a "hit post" until 4 years after i started doing digital art...) but if you wanted any thoughts on that please lmk. i find my answer to this question kind of a non-answer........ but i hope it was interesting at least!