These pump and dump schemes steal money from wannabe investors, and that is the end result which ultimately counts. So if some or even most of these 5,067 altcoins are not technically dead (read, delisted from all important exchanges), this doesn't mean they are not left for dead with the orderbooks empty on the buy side (read, there are no more idiots left willing to buy these shitcoins)
Altcoins are in no way promoting Bitcoin. Bitcoin is standing on its own and do not need support from these Altcoins. Experienced and knowledgeable people always go for Bitcoin. Beginners choose Altcoins for trading as they do not know much about this market, and so is the reason why they get caught by the net of scammers. In the end they do not get any kind of benefit so Altcoins cannot compete with Bitcoin
As you can see, opinions vary on this subject
If you follow the thread and read the responses posted here, people are expressing quite the opposite views. Personally, I agree that the net effect of altcoins on Bitcoin (and its market valuation aka price) is negative. To make things abundantly clear at this point, I'm talking specifically about the
net effect, i.e. all things considered, weighed in and accounted for, which means that if only Bitcoin had existed, and maybe a few other altcoins that pick up where Bitcoin leaves (as there are many dimensions to what a cryptocurrency can do), the whole market would have been in a far better shape than it is now
Well, that is not to say it is in a totally bad shape today, but just picture how it could be if people hadn't been losing money all this time. But likely too much of a good thing, though (read, never happens in real life)