Sadly, the Pokemon series is stuck in a situation where it doesn't 'need' to innovate or do anything ambitious to sell well/get good reviews, so its creators basically don't bother and coast along without trying too hard. It's kinda like YouTube under Google to be honest.

Extremely high levels of popularity + no competition + unambitious creators that are out of touch with their audience/userbase can equal a mediocre product or series that just ticks along without any attempt to live up to its own promise.