Interesting take. But Moore’s Law is still on the side of (some kind of) proxying. So long as your legacy system ran for at least a few years (it did, right?) then you’d expect to be in a reasonable position to emulate it, all being well, by the time you’re replacing it. Or move it behind a reverse proxy (reverse proxies are so fast these days that people introduce third-party doglegs like Cloudflare in order to gain their other benefits), whichever’s appropriate. For some legacy applications, such a move can actually be an improvement, e.g. there are sometimes performance benefits in emulated filesystems or in caching reverse proxies and there are often security benefits in adding a more modern, patchable system in front of your old, hard-to-maintain one.
I’m not defending the author of this piece completely, mind. I’ve also done reimplementations that were absolutely the right choice. But I agree with them that rewrites are overused.