You think delays, being slow, and constant "resuming" and "loading" represent critical errors. Nobody in the software industry would agree with you, but you're entitled to your opinion.
A critical error/bug is a literal show-stopper. It's a feature that should work but doesn't, and ends up making testing impossible or meaningless. This is the definition typically used by anybody in the industry, including those who finance custom software development but aren't developers themselves. Having to wait longer than you'd like for an app to resume doesn't qualify.
Granted, substantial delays can make testing a pain in the rear, but if you CAN test it, then there is no insurmountable (critical) error.
Lastly, what you think should be fixed in a matter of days and prompt MS to release a new build ASAP, may very well involve a team of people working for one or two months on SoC optimisations. What you want may simply not be possible. At least the loading/resuming issue is likely systemic, for which I doubt there is a quick/easy fix.
Anyway, the point is this: you can rant all you want, but you won't get anybody at MS (or Apple, or Google, or anywhere else for that matter) to change their mind on this. The only viable alternative would be to NOT deliver a preview at all. If a majority of people adopt your view, canning the insider program is MS' only reasonable alternative, because your expectations are not realistic for software in this phase of its development.
This we agree on. Apparently we disagree only on the definition of the word "prevent". A computational delay can't prevent you from testing anything. The critical error here is actually your impatience, which is easily remedied by going back to WP8.1.
Actually, finding and reporting bugs isn't the primary purpose of the insider preview. If that's what you're doing you're wasting your time. MS has their own professional testing staff that delivers far more useful, reproducible and actionable bug reports than the community ever could. What you should be reporting on are things you do or don't like. That is far more interesting to MS.