I agree I will not even think of optimizing my code to run on POWER, SPARC, or ARM and that I won't care where my software runs enough to create a market for these, but I don't care enough to keep an x86 market either.
Having said that, it would be good for those who propose new architectures to ensure there is a ready supply of entry level machines for enthusiasts and early adopters. Seeding these groups will ensure their architectures and software is more thoroughly used and tested.
Games on smartphones are perfectly viable - RPi is not good enough but oDroid or Google Pixel is.
The only problem is developing on same machine as you use. For that, you need a full fledged, quite powerful ARM laptop. Hacked Chromebook for example. Otherwise, the emulator is way too slow.
Linus very much sounds like a grumpy old man saying "get off of my lawn!" (as he usually does).
Plus, server space buyers are conservative, they want support of a big company behind their hardware. Someone the size of Cisco, Dell or HP. Or hardware that is used by Google or Microsoft.
Combine that with anticompetitive long term agreements and you get the picture.
Somehow network routers have a variety of architectures inside and nobody has a problem - because they have a bunch of reputable companies behind each of them. (Variants of MIPS, ARM, ARM64 and x86 are in the wild.)