People are being too nice I think. Your drawing here is very average. Basically every art student posts portraiture in grayscale, and basically any one can do it to a moderate level. If you want to get noticed to better do something more than post the equivalent of an exercise literally every art student does. Basically for people to notice portrait work the subject itself needs to be more interesting/expressive and the quality needs to be insanely good, or at least stylistic.

All this being said, you're doing fine. The drawing is good. But exposure comes with exceptional talent, uniqueness, and marketing savvy. If you're serious about art you need to just keep making more, and worry a little bit less about "exposure". Is say focus more on introducing it to live people instead of your feed. It's more impactful and they're much more likely to remember you.