The term "meme coins" has been used by many investors and became popular hence, it was called meme coins, but you're right.
Meme coins doesn't have it's own blockchain "EXCEPT" Dogecoin that has it's own blockchain already, and Shiba Inu is the next on the list (based on a quick google search).

Just imagine calling them "meme token". It's a bit awkward at least for me because the it has been called meme coin and it became popular. To sum it up, a meme coin being called a coin or a token doesn't matter for an average investor especially if they believe that they will make profit in investing in meme coins. Nobody cares whether it's a coin or a token. What matters is profit for most investors. That's the reality.