I agree. A rating and review system will be a major improvement in addition to sort by date first published or last updated. It would also open another channel for feedback about a plugin other than opening a GitHub issue which most users may not do.
Now that I think of it, implementing a rating system would require an account of some kind to track who gave the rating or wrote the review. And since Obsidian itself needs no account, this would be tricky. Maybe Obsidian Forum account can be used to track the ratings and reviews.
I found another post requesting such a feature but it was incorrectly posted to the plugin ideas category: Have a simple review system for plugins