Participating in a critique group is absolutely the best and quickest way to improve as a writer.
Many people think that the best and quickest way to improve as a writer is to write. This is not true–but you should still write as often as you can. Or some might point to the legions of craft books out there. By all means, read them! Read as many as you can. Watch BookTube videos, participate in BookSky discussions. But, again, this is not the fastest way to improve. Any of those will give you a good entry into writing, will explain things like structure and character arc. But you will not fully grasp those things until you apply them, and the quickest way to apply them is to use them to critique the works of others.
Say, for example, you have read Stephen King’s On Writing. In it, he makes the case for weeding out adverbs. Now, adverbs are important. All of our words relating to time are adverbs, and he doesn’t mean that you should get rid of words like soon or yesterday. He refers to adverbs that end in -ly. He says you should change It smells really bad in here to It reeks in here. He’s talking about punching up the verb so you don’t need the adverb, which makes your story more engaging, does more showing than telling, and decreases a bloated word count. If all you have done is read On Writing, you may not completely understand what he is saying. However, if you’re reading someone else’s beta draft and you come across a lot of adverb bloat, you’ll start to notice that it bothers you. You will then explain to the writer why it bothers you, and in doing so, that explanation that you write to the other writer will clarify the issue for you and help you improve your own writing so that you don’t make the same mistakes. I have had this experience for everything from character development and arc to sagging middles to, ahem, adverbs. It is absolutely* worth the time to be in a critique group, and you may end up with several lifetime friends in addition to developing as a writer.
*Adverbs aren’t bad. Sometimes you do need to punch up a verb. But use them deliberately!