Not that this is different from perhaps any other platform, but it's exceptionally difficult to grow a following as an artist on Instagram. It was probably never meant for it, but instead more targeted towards influencers. Visual artists with hundreds of thousands of followers who didn't buy them or didn't inherit them from fame outside of IG are practically unheard of.
It is possible. You just have to post consistently and use the right tags. I'm not famous and I can get 10K followers just by posting one every few weeks, sometimes I post more regularly. More followers are gained when I post more often. In short, work.
Baloney. You can get 10K followers at that rate, in maybe five years. Once every few weeks is basically a dead account. Even posting daily, you still have to use all of the tricks. There is just so many people doing the same thing on there, that you have to be VERY niche, and put up quality content. Food photos, in poor lighting, from your phone, are not going to do it anymore.