So, you were on the smaller ships. I sailed on the Imagination once and I found trhe dining room to be excellent - probably the best thing about that ship, and our waitress was amazingly fast and efficient. (a lovely Asian young lady, as I recall, but she spoke perfect English).
Yes, once you move up to the bigger ships you run into a different level of service because there are so many passengers onboard.
Well, every cruise is a learning process to figure out what suits you the best.
I don't know you personally; but it might help to read some of the comparative reviews of the cruise lines and see if another line might be more your style; smaller ships, more personalized attentive service.
Some of the smaller Princess ships, or Holland America, for example; are often priced about the same as a Carnival cruise but the onboard atmosphere is more subdued, less revelry and more attention to service detail. Now, I don't know if that is what you want but my point is that Carnival is unique brand and one should not judge "cruises" in general just based on Carnival alone.