Since you clarified in a comment that you're wondering whether questions where you would...
paste like a part of my writing here and ask for comments about my writing style and suggestions on how I can improve
...qualifies as a critique request, and thus would be off topic, rather than asking simply whether critique requests are on topic or off topic.
I would strongly argue that such questions fall under the critique request umbrella, and are thus off topic on Writing SE.
Here's why: The decisions to classify as off topic both critique requests and proofreading requests were based on the fact that such questions will be useful only to the one person asking them, and that there is generally no good way to determine how well any given answer actually answers the question.
Questions that are only useful to the one person asking them and questions where it's hard or impossible to judge how well an answer answers the question are a poor fit in general for Stack Exchange's Q&A format. A question should provide some kind of lasting value; as a rather contrived and admittedly perhaps somewhat extreme example, that's why, for example, you can't head over to Seasoned Advice and ask about what to make for dinner. Critique requests aren't all that different in that there's typically a potentially large number of equally valid possible answers which can't be objectively judged, which makes them primarily opinion-based, and also that the question provides little value for anyone other than the asker, and even then likely only in the moment – we just happen to have a more specific custom close reason established for, among other things, critique request questions.
About critiquing specifically, it's also difficult to get a feel for someone's writing style from only a few paragraphs. That's not an insurmountable obstacle, but it potentially reduces the usefulness of any advice thus gathered.
That's not to say you can't discuss those things at all. We even do have a specific exception which sort of allows for something similar:
- ... However, please do feel free to use your own writing as examples in on-topic questions.
Note the emphasis: examples. The question needs to be answerable without the example; examples are for clarification only. It's really not much different to how we don't like answers that rely too heavily on links to external material; it's fine to include links for additional reference, but the answer should at least be meaningful (and ideally at least moderately useful) even without following any of the links. Same with questions, which shouldn't rely on people following umpteen links to figure out what someone wants to know; questions that rely too heavily on external material can be unclear for that reason.
Alternatively, this type of question that likely involves significant back-and-forth is one thing that our chat room can be used for. Chat isn't terribly active in our case, but there's no rule that says it has to be that way; it won't get more active though without participants.