I understand what you mean. Yes it was painfully obvious that iOS 9 was not optimized for the iPad Pro. It does look goofy with the widely spaced icons... making it look more like Fisher-Price's "My First Tablet" for preschoolers than the top-of-the-line iPad. Lots of wasted space in apps that don't take advantage of the larger screen.
At MSRP, I thought the 12.9 iPad Pro was (and is) overpriced for what it does. I only bought one when there was a significant percentage-off sale. I am enjoying it, and it is doing what I expected a giant iPad to do. So no surprises or disappointments there. I think based on what you've written in this thread, I think you and your husband feel the same way... the current functionality is fine.
But... with extensive use of the 12.9 iPP, it becomes obvious that this beast (in the good sense) of a tablet has so much untapped potential. A little tweak here, a little tweak there, and this thing could be so much more. For some of us, just a few minor adjustments to iOS and a few minor additions.
So to watch the iOS 10 reveal be nothing more than Emojis, shared clipboard, and split-window Safari tabs is indeed disappointing.
For me, the iPP has essentially replaced my 11" MBA and iPad Air 2. It supplements the iMac in my home office. I'm not letting Apple's lethargic pace of enhancing iOS for the iPP prevent me from enjoying all that it does and what it can currently do. I've received a Citrix X1 mouse that works with the iPad (within Jump Desktop only) so that I can access OSX on my iPP using a keyboard and mouse.
I can do this with great confidence in spite of the situation, because the alternatives are far worse (IMO). How do I know that? I've used them extensively.
Although iOS 10 hasn't been released yet, the "highlights" were announced at WWDC last week. Shared Clipboard and Emojis-R-Us were the "stars" of the iOS 10 reveal. While it is possible that Apple has some whiz-bang iPad-specific updates up their sleeve that they haven't announced yet, based on what Apple has chosen to show us, there is nothing that is optimized for the iPad Pro... oh, except being able to have a Safari tab open in each window of Split-screen.
So yes, it is reasonable to be disappointed in iOS 10 based on what is publicly known about it. If Apple reveals more, then reasonable people would factor that new info into their opinion and adjust accordingly.