Everyone has different storage needs so please withhold your judgment on what you define as "ridiculous." That being said, the iPad Air is still currently Apple's flagship tablet.
The iPad Air is still currently Apple's flagship tablet, but it doesn't cost $700, it costs $500. It's $500 that has "issues" you described, not $700. The additional price you paid has absolutely nothing to do with these issues. You can buy a $1M+ Mac Pro painted in red by Sir Jony, but it will have exact same issues as a base model.
So you paid only $500 to have these issues, not $700, ok?
That said, the perceived slowness might be simply related to animations. Perhaps, Apple deliberately made animations on bigger screens slower so you can be delighted with them more.