We have a Screenwriting forum in our Share Your Work area (see sigline below) where you're welcome to post pages and/or read stuff that's already up for critique.
The Share Your Work forum here can be helpful, but getting feedback on ten page chunks of your script - totally out of context - is not the same as getting feedback on your entire script. Things like plot and character development, pacing, conflict, stakes, structure, thematic exploration, etc. cannot be assessed in such a forum.
Not to mention the fact that the feedback you get on a board like this comes from people who run the gamut from very knowledgeable and insightful to those who have very little understanding of the craft.
I think feedback here is good for getting a sense if a scene or sequence is working or if your writing is polished enough, - but it's not good for assessing whether your script is ready to go out. A submittable script needs to work as a cohesive 100 page story. It needs to work as drama. It needs to work as entertainment. And that can only be assessed when looking at the whole script.
There are hundreds of options out there for professional feedback. You can pay as little as $75 for low-end coverage to as much as five or ten grand - for notes and coaching from the grand poobahs like Linda Seger.
I don't recommend coverage, because generally speaking the "readers" who do coverage give a thumbs up or thumbs down on whether scripts should move up the ladder, but they aren't tasked with the responsibility of finding ways to improve or strengthen a script like higher level development people are. So if they pass on your script, they often don't give you the info you need to do the work so that they would recommend it in the future.
You can get notes from higher level development people and/or produced writers for 3 or 400 and up. These notes are more about identifying the specific problems, and with the better ones, offering solutions. These people also tend to have a better understanding of the craft.
Some of the consultants that provide notes can also provide access to agents, managers, producers etc. This allows you to bypass the query process and submit via referral, which not only makes it easier to submit, but can also lead to your project being read with a totally different mindset.