You have a lot to 'unpack' in your question: beginner, self-taught, opinion, review, criticism, copyright.
I'll skip the copyright part. That's law. Read up on that and handle your music accordingly.
Some personal observations:
Music professors will offer technical advise on the craft of writing. From an emotional perspective they will encourage you to keep writing. You are more likely to hear something like 'you did this here, but you could also have done option 2 or option 3.' You probably won't hear 'you did this here and it moved me deeply.'
Students will offer all kinds of emotional reactions. But, it typically goes two ways: the praise for you that they really want to hear about themselves, or the harsh payback critique from someone you have criticized.
Friends and family will usually say something like: 'that's nice.' Occasionally, you might get 'I could never write music.'
All the above are generalizations, but based on real experiences.
Once my wife voluntarily said she like a 'Gay 90's' style waltz I wrote.
The only real emotional comment I ever heard was from a co-worker/friend who listened to an 8 bar, minor key, exercise I wrote. He said: 'damn, why you gotta be making me cry!' From the perspective of craft I have no idea why I got that reaction. It was an electronic playback with strings and oboe, slow tempo, and some non-chord tones.
Those were nice compliments, but in terms of development it didn't help me much.
So, having shared all that I think you should ask yourself this: as a beginner what exactly do you want? Do you want the kind of feedback a professional would give? Do you want emotional feedback with no insight to the craft or worst is not genuine?
Of course that question is rhetorical. My advice is to get the advice of professionals or at least those with a serious approach to learning the craft.
Try to distinguish between: opinion, criticism, review, etc. Mere opinion is not objective, an audience of one. Formal criticism should be de-personalized and based on some objective understanding, the realm of the professionals. A review is written to inform the public, it could be good or bad, but 'there's no such thing as bad publicity.' Online followers, likes, etc. I would put in the review category, because in the end those are about publicity.
Wanting feedback from lots of people is a natural desire, but I really think it is more important to develop a good sense of self criticism. Good teachers should advise you at a level appropriate for your level. The more you push yourself, the deeper the advice you can then receive. Seek out quality relationships not the greatest number of commentators.
Two final anecdotes.
After college I kept studying. Eventually I mailed a collection of short pieces to that composition professor form college. I think I attached a short letter, but I can't remember exactly. I didn't know if I would get a reply. To my surprise he telephoned me and then wrote back a short letter. He gave me a few tips and words of encouragement.
More recently I send some 'cold' emails to two professors who wrote theory books I really like. I explained how I was trying to apply ideas presented in the books to my studies. In one case I attached a score for a sonata exposition. I received replies from both professors including a copy of my score with revisions from the professor.
I took me a long time to build up the nerve to approach those professors as I was not one of their students. I made sure to be brief and specific and appreciative. No vague questions. No nagging follow up emails.
You could try reaching out to people this way, but make sure you start with critiquing yourself.
