The conversation what role alts actually play, has so far only been along the lines of "it can do things that Bitcoin cant" or "its a test-bed for Bitcoin" etc. To some degree those claims are valid, but how many alts does it really need to carry out those so-called benefits and alternative ways of doing things with the blockchain? Surely not 500+ can all be for the benefit of exploring different uses of blockchain tech. That just cant be true. So somewhere, a large part of creating yet another shit-coin, is for either self-enrichment, or, just because you can, or, a deluded self belief that you have 'the one', or vanity etc. In all these cases, its not only wasting resource, its plain to see its also self-destructive, ultimately.
Miners understand efficiency, latency, redundancy, profitability, and obsolescence. Hopefully they can apply those same concepts to systems larger than a mining rig.
If two altcoins are doing the exact same thing, one of them will probably be orphaned. Everyone who had that altcoin will get nothing.