There is no doubt in the fact that altcoins have helped in the publicity of the cryptocurrency industry and their various hypes have helped to bring cryptocurrency into mainstream awareness, even though we can't deny the fact that, altcoins have also influenced the negative perception about the true intent of cryptocurrencies like bitcoin which provides better alternatives to fiat and as a good asset to hold.
And also some of the altcoins have provided some specific services that contribute to the scalability of the cryptocurrency industry and make the transaction easier faster and more flexible.
The fact that even if it was rare, some people made a lot of money via altcoins allowed people to think that it was possible to get rich, which brought in a lot of people. This had one good thing and one bad thing about it, good thing is that there were a lot of newbies who were interested in crypto in order to become like those people who got rich and they wanted to replicate that luck, the bad thing is that most of them failed and they lost their money so they are doing terrible at the moment.
This is why it's both a good and bad thing together, a lot of money got in, but a lot of it changed hands, if it ended up with people who stayed in the crypto world, that's good, but if it ended up being cashed out then it wasn't a good thing in the end.