So, I'd say the places you're posting stuff is a good broad mix that will attract readers who might be looking for stuff like yours. Of which there will be some, but not so many, probably. The tricky part is finding the ones who aren't looking, but would be interested if they knew your story existed.
The way to get to those people is too go looking for them. I used reddit and found a large audience eager to try new stuff (and also eager to tell you what they don't like). Because I write fantasy and I discovered web serials through translated Chinese/Korean stories, I posted chapter updates on r/noveltranslations, which allows original English novels too. The reason I chose there was because the audience is huge. While my story might get a couple hundred thousand views a month, the big Chinese ones get around 10 million/month. That's the English, fan-translated version. God knows what the original Chinese version gets.
Those readers are keen to find stuff without poor English and bad grammar, but they're also picky about what they like (often immature stuff about OP MCs). There are non-fantasy stories up there, but it would be worth having a look at the EN novels posting on there to see if you think your story might fit.
And yes, I posted myself. Self-promotion is frowned upon in a lot of places on the web, but those are the places not to self-promote in. Reddit subs have rules and the ones I'm mentioning allow it. You should always check first.
I also went to places like r/fantasy, and like most of the bookish subreddits it has a special promotion threads you can post in. For you r/scifi might be more appropriate, I know they have weekly self-promo threads. How much response you get will vary, but it's worth having a look. It's easier if you also find the sub genuinely interesting and interact with the other threads. Also r/rational might be worth a look. If your story has a strong rationalist element (people do things in a realistic and rational way) you should make an introductory post announcing the story and then see if there's any interest. Hang out there a bit first to get a feel for the place.
r/writing and r/selfpublishing also have self-promo threads.
You aren't going to get a sudden tsunami of readers, but one or two will get the ball rolling. I've now started to get people posting updates of my chapters on r/rational without asking anyone, just because they wanted to.
Interacting with the people and threads (and they will mostly be relevant to your interests anyway) will work much better than dropping a link and running away.