I'd like to start this by explaining why I rejected that edit.
I rejected (and edited) that suggestion1 after I have approved (and edited) 3 suggested edits by you consecutively: 1, 2, 3:
1st suggested edit: image resizing is mostly welcomed (due to the current notorious buggy Imgur's image scaling), though the title shortening and the addition of Android version tag were questionable. The suggested title would make the question too general, and there's no indicator that this was specific to Android 8.1. However, I decided to err on the side of caution and approved the suggestion as good intention, then clarified the title, removed the tag, and added a more relevant tag.
2nd suggested edit: the suggestion added paragraphs to make it more readable, fixed some capitalization, and clarified the steps. Though there were some missed capitalizations ("chrome" on the first paragraph) and typo on the name of the app ("Pintrest"), the overall suggestion was good and hence my approval. I also took a liberty to fix the rest & remove fluff that I feel didn't add anything to the answer
3rd suggested edit: fixing code formatting properly is welcomed, though I wondered why you didn't fix all capitalizations and punctuation in the beginning. I decided to approve for the code formatting and edited the rest.
4th suggested edit (1 the review preview is misleading because only the title was changed, compare to the original revision instead): the suggestion only fixed the title. Ignoring the fact that the editor couldn't create a new tag (which is understandable), while the title fix was an improvement, I couldn't ignore the rest that none of the capitalizations ("android", "i") and the spacing after punctuation were fixed. At this point, I decided to reject and fix all obvious issues. The fluff removal was my personal judgment. Had the suggestion fixed all the obvious issues even without removing fluff, I'd approve it.
I understand your good intention on improving this community by suggesting edits, and I really appreciate it! However, the help center on 'edit' privilege (2000 reps) mentions this
Tiny, trivial edits are discouraged - try to make the post significantly better when you edit, correcting all problems that you observe.
(italic emphasized mine)
The first 3 suggestions were certainly improvements to me, and that's why I approved them. However, the last one... fell short to me, and hence my decision to reject it.
Now, please don't be discouraged due to that rejection, keep up on suggesting edits! But I'd like to also take this as an opportunity to let you know about this and edit more carefully from now, and we'll have a win-win situation :)
Now, for the rest of the meta question
When I started with editing posts, there used to be many of them rejected because I only changed capital letters or corrected a few grammatical errors or formatting that were not considered not good enough.
Personally, if I faced the "capital letters" review independently, I might have approved it (though I could also see the edit as too minor). However, it might be a similar case to this when you suggested many consecutive edits with some questionable quality and made the reviewers wary about the edits.
The "formatting" one was an edit conflict, so it's not really your fault (and it's an acceptable edit too). It's just that someone with full edit privilege was editing the post at the same time, overriding your suggested edit.
There is a question in StackExchange that deal with whether "Thanks", "Thank you" and such, should be kept or removed (edited out) on questions.
Should 'Hi', 'thanks', taglines, and salutations be removed from posts? is always a controversial topic. Some agree that those are noise that doesn't add anything to the post, but others disagree because of social interaction (and to the extent of the recent "SO is not welcoming" uproar). While I'm on the side of "no fluff", I don't strictly enforce this policy to others. It's up to personal preference.
Why are they (the edits from moderators and high reputation users) consider better? How does the edits that would have been rejected when made by a new user or user with a low reputation be accepted when moderators and high reputation users?
Please don't take it wrong. Edits done by moderators and high reputation users (2000+ reps who can edit freely) are not always considered better. Sometimes they still make mistakes (I believe I did) because they are humans too! However, their edits are automatically applied instead of being put into a review, so they might look like "better".
However, consider the previous guideline from the help center: "Tiny, trivial edits are discouraged".
Since users having less than 2000 reps get their edits reviewed by other users, consider choosing and editing posts that really need to be fixed. For really minor typo and grammatical issues, you might be better in posting a comment to let the OP or other users fix them.
Fun fact: I learned today that Community is able to reject edit.
The Community (bot) user is able to reject edit when either an edit conflict happens (an edit suggestion is overridden by other user's edit), or when someone chooses "Reject and Edit" from the review. On the other hand, it is also able to approve edit when someone chooses "Improve Edit".