Not just an opinion, but a sharp-tongued poke at a sacred cow. I would be singled out as negative, not a team player, a troublemaker. I'm welcome to have an opinion, as long as I don't make waves. Keep your head down and do your job is the motto. The "leaders" set the tune and you march. If they tell you to jump to Agile, all you're welcome to ask is "how high?"

In a lot of companies it's similar to voicing an opinion about an alternative religion in an area dominated by one "true" religion.

Not to mention the fact that various job titles (scrum master?) are tied to the existence of such process within the company and are not useful outside of the context.

Most corporations will fire you for voicing certain (non-oppressive) opinions, since ideology is important. You see it in schools too, not to mention cults. You're allowed to get to the next rung by not seeing it, already having the right attitudes, or faking it. (Consider some meanings of "cultural fit".)