From 2018 to 2021 more and more altcoins are circulating in the market, but not all of them last long and make good altcoins, only a few altcoins can provide positive value to the market industry. From the many altcoins launched, I think it will have an impact on investors so that investor interest will decrease if they take the wrong steps or invest in scam coins.
There's no denying about the increase of altcoins, but the question is not the quantity, but on the quality.
Here's a complete graph to see a bigger picture, https://www.statista.com/statistics/863917/number-crypto-coins-tokens/
look at that, what percent do you think are real projects with future potential?