There unfortunately isn't really a perfect setup in the Apple lineup (or anyone's lineup), as you're discovering. While the price of the MK does come close to another iPad, I'm not sure owning two iPads is really worth the hassle. The MK was worth the cost to me at the time as I used my 11" iPad Pro as my main computing device for almost two years, and I enjoyed the hell out of it. The MK certainly isn't built to last though - I had mine replaced just recently a bit after the two year mark. It was through Apple Care so no cost, except to my sanity while Apple support kept telling me over and over that it wasn't covered (it IS covered).
If I was still using an iPad Pro as a main computing device, honestly I'd probably still get the MK all over again, because it's just such a good experience vs everything else, and because I'm not that bothered about having every inch of my iPad protected all the time.
The 14" MacBook Pro that work got me has converted me back to the Mac for now, however, so I don't worry so much about the MK, and my iPad Pro spends its time in the smart folio these days. The MK is now reserved for those times I'm travelling light and I'm taking just an iPad with me. It's the perfect setup for a long flight.