This is why scientific and commercial mainframes still exist, and why a lot of computing is offloaded to cloud services, relegating the modern OS on a modern CPU to a client system.
There are also entirely classes of fairly conventional applications - A(G)I, true holographic displays, pseudo-real telepresence, real-time photo-realistic rendering (although that's starting to become possible), distributed non-localised filesystems, associative semantic storage of all kinds - that modern hardware is still too slow for.
And more speculative classes too.
In fact contemporary hardware is mostly quite slow and dumb. It's incredibly fast, small, and cheap compared to a mid-80s mainframe, but it's going to look very underpowered and crude fifty years from now.
On modern pc/server/mobile computers it's impossible, your root of trust there is manufacturer and their microcode/embedded security modules with separate operating system etc