Blame the tire not the rim. I avoid tires that are too difficult to mount. Not worth the trouble so I never buy that tire again. I don't want a tire that is so hard to mount that if I have a flat I would have great difficulty on the road switching out tubes.

I can't see me being able to use my thumbs to mount the tire pictured by the OP. I use tire irons in this case and do it very carefully to avoid pinching the tube.