@Pokari
There are three pretty major flaws to that argument.
1. If it's necessary for him to go down an initially weaker evolution tree, that's fine. But the story needs to give the character motivation to do so. And by that, I mean more motivation than your mom nagging you to take out the trash.
2. There's no reason why a "dragon" needs to be a powerful being. This is a fictional world of this author's fantasies. If he wanted dragons on the bottom of the food chain, there is no reason why he couldn't establish that. Just think back to spider, she's not just some conventional spider. She's got unique abilities and magic because the author had the freedom to write whatever he wanted.
3. My use of the term beta does not mean that the opposite would have been an alpha. What he is now is not "beta" as in meek. Rather, "beta" as in an autopilot with no brain. Maybe that doesn't justify the use of the term beta but I couldn't think of anything better at the time.
I really don't want to believe that I have to now justify to people why characters need to think. But then again, this is isekai and the protags usually don't need to think so whatever.