There are a number of sites out there, some free, some subscription-based. Most involve swapping work. That is, you critique my novel, and I’ll crit yours.
I’m a member of Scribophile, a writing community I’ve recommended before–see my description of their crit process here.
If you are at all interested in Scribophile, I recommend signing up for the free plan and browsing the site. Read critiques of the works of others, looking for critiquers whose feedback is insightful, at the sophistication level you are targeting, and in the genre you are targeting. These are the folks with whom you’ll want to network and swap crits. (Scrib is as much a networking site as it is as work-sharing site.) Essentially, your goal is to find other writers who would also be your ideal readers.
Check out the forums as well. The publishing forum is full of questions such as yours. The forums are also a great place to find like-minded writers.
The benefits of the paid plan made it worthwhile for me, but there are plenty of active writers there who are on the free plan.
Best,
Jim