I tend to support the assumption that they increase the awareness of the crypto space, as they're a "fun way" to enter a world which often is associated with nerdy geeks and wannabe pro traderz At least this should be true for memecoins like Doge which are not simply a tool to enrich their founders. So in theory users could "trickle" into the crypto space and eventually will "land" in the arms of the safest and biggest one, Bitcoin.
The memecoin wave which started (?) with Ordinals, (or at least I'm aware of it since then), where the creators let random people "mint" coins until a certain limit, however is economically totally useless and very prone to scams, as nobody knows how many coins were already minted by the creator as he can use the number of addresses he likes and thus fake an "even" distribution and high popularity. Only few coins really circulate and that makes price manipulation to the upside easy. Even a premined memecoin (with transparent tokenomics) is probably often fairer.
These practices of course lead to disappointment and so I can understand the opinion that memecoins are actually harmful, too.
I'd like to read research about that issue: do memecoins enrich the crypto ecosystem or not? While I have found some papers on Google Scholar about the "co-explosivity" in price (i.e. that Bitcoin and memecoins tends to "bubble" at the same time, and Bitcoin price unidirectionally seems to influence memecoin prices) but nothing really on a longer-lasting influence of memecoins on Bitcoin adoption. An interesting find was instead this study, where memecoins were found to be a possible "hedge" for Bitcoin crashes
This study which explores behavioral patterns on social media which may influence memecoins, meme stocks and Bitcoin prices may also be interesting but is not freely accessible.