I didn't notice anyone giving this critique so I'll go for it-
Trying to work around algorithms aside, there is a good chance of when/were you update VS were/when your audience checks in is in completely different time and places. Its very common that all the big sites tend to share the same general audience groups- but which ones are bigger and more active varies.
Personal example- SmackJeeves gets joked a lot for being basically a PMD site. If you write/draw a PMD comic, your best bet for your audience to find you is to upload there, regardless if you like the set up of the hosting site or not.
There is also generally spreading out and saying hello in other places. Kind of like what you are doing right now! But going to large sites like Reddit and finding the subreddits that cater to your themes is paramount. Most of my audience has found me from linking my work to reddit.
If all of that is tried and you feel algorithms are still not with you, fanart can help your audience find you. No, not just any fanart- fanart from works that have directly inspired your own personal work. People thirsty for those shared themes are always looking for more. I noticed you have some Earthbound pieces, perhaps sharing links to those pieces on various fanboards will help!
There is also the fact that said Instagram has only 20 pieces right now. That's 20 chances in a crazy large ocean for people to find you. To expect to grab a sizable audience with so few pieces is expecting the craziest amount of luck.
Wish you best, figuring out how to get your audience to find you is one of the hardest things as an artist.