This is an acceptable answer, as in we would not remove it as Not An Answer. Whether it's helpful to you or not is another matter entirely and is something for votes to sort out (this answer is helpful / unhelpful).
Homebrew review questions are just normal questions. Your question asks only “Is this homebrew balanced?”. That answer responds on whether or not it's balanced and is therefore a valid answer.
Your question does not request advice on how to make it balanced. This means providing such advice is optional, and answers doing so are going above and beyond what you've requested. Answer authors should aspire to do this if/when there is advice they can provide since, if the advice is good, it will make the answer more useful and earn them more upvotes. But it's not required.
There are no invisible rules about how to answer this kind of question any more than any other question, nor should there be—invisible rules worked out really badly for rules-as-written, and the weight of unstated requirements made designer-reasons questions a trap waiting to ensnare the unwary. So we have the default rules for how Q&A works: ask what you want to find out, and answers respond to what you asked.