When people saw the value of Bitcoin, they also created various altcoins. It will run away after harvesting and have no real value. Although these coins are not reliable, there will be some people who are willing to bet that altcoins can explode. Some people who make a profit from investing in Bitcoin will also choose to invest in altcoins.
In such a messy market, how should we invest in cryptocurrency? What should do with these altcoins？
You should not judge and generalized all these alts. First is that many alternative coins are used and have utility that determine their prices. Some of this alt coins are even richer in feature compare to Bitcoin. I know many projects are coming out scam after being successful and that's where our investigative instinct should appear.
Altcoins that are high quality usually indeed have a product to offer and these product offer real utilization for the coin so its not right for people to undermine Altcoins.
The rampant release of Altcoins is nothing but just a normal phenomenon where people trying to make their own coin while also offering product but the market will select which coin deserve to have value. It's not a problem for altcoin to be consistently released.