Yes, exactly. Your post points out, correctly, that boosting is the only way to increase a post's visibility.
I'd like to point out one thing explicitly for newcomers accustomed to other platforms that count and display likes/stars for everyone to see. Mastodon doesn't work that way. A like/star is only visible to you and the poster. Nobody else knows that you clicked the like/star. As stated in the OP, boosting is the ONLY way to increase visibility.