I can't say I have experienced those issues between Odysseys and Siennas, but those are quality problems, nothing inherent to the concept of a minivan. I don't believe a minivan is or was underpowered for 99% of people's needs, especially to move family in a 1 hour radius.

It's funny that you point out Japanese companies as the actually worthwhile minivans. You're not pointing out the shitwagons dumped out there by Ford, Dodge and Chevy that were the bulk of the market. I remember the Astrovans being especially bad. There was a lot of stumbling around by US makers switching over to things like fuel injections and electronic controls. A lot of this left some amount of consumer dislike to particular brand names. Then when you add that SUV/Crossovers started showing up when manufacturing of cars had improved greatly these new models were more apt to be considered quality it made a big difference.