Not all new altcoins are bad. I found many new altcoins that already gained huge fame, volume as well as included in top altcoin list in 2023. So for bnb. But the fact is, finding good coins aren’t easy. Someone may advice a bags of "rules to find out new good altcoins" but that won't work as we expect and no surety at all. It also depends on luck but most of the time people fail to find the good one. But if you can, then you are welcome to invest in new altcoins with own risk
The problem with crypto market is that its highly unregulated and there is no way you can certain that new coin is legitimate or not. You have to take risk of investing in new coin and it may or may not be profitable. As far as old alts are concerned, to me only top 20 alts on CMC are worthy for investment. You can DYOR on new coins but still there is no gurnatee of there future. I would say if you have to invest in alts then invest 20 to 30 percent of your capital in Alts rest should go for Bitcoins.