Decent bike, if the particular design compromises (Lefty fork/650b only setup/no rack or 'guard mounts) aren't a problem for whatever you actually want to do with it. Ted King won the Dirty Kanza 200 on a Slate and has nothing but praise for it. Wheel changes are not a problem with any through axle setup, that's utter twaddle. Mr King somehow changed three flats in that race without issue…as do many thousands of others. All these press-fit BB 'standards' can be problematic, there are more variables than can lead to the dreaded creaking, reduced service life, and so on…but a properly sorted setup is no bother whatsoever.
Rough guess is you're not looking for a CX bike, but a gravel/all-road/adventure/what name can some other marketing dept. come up with bike. Of which there are many, many good ones. Apart from my own Litespeed T5G (now with flat mount brake setup), there's the Tripster ATR, the Grade, the Datum…most of which will be a bit more versatile than the Slate, will take 650b wheels as well as 700s if you wish, and can do duty as fast road bike/off road bike/commuter/all of the above. Think about what you actually want to do with the bike, do your research & you won't go far wrong.