i had a desktop from 2006 that i replaced and my laptop was crushed by movers so i had it replaced. two new machines.
Ditch the desktop, get an external monitor.
even if i had two of the same machines, it wouldnt be a waste. i like to use one machine as a sort of home media server.
I never count my server or my NAS as one of my "machines". They're network infrastructure, not my PC.
second, some people have spouses and children which sometimes demands for a 2nd machine.
My GF's machine is her machine, not mine, even though I bought it for her.
when i get back home next year i will buy a mac, which is probably wasteful but i want to try something different. if i dont like it, i always can give to a niece. aka recycle.
Wasteful as in wasting your money. At least sell your current machine before buying a new one.