"Hi, I'm Kent C. Dodds. I'm a world renowned speaker, teacher, and trainer ..." - https://kentcdodds.com/info World renowned is an extreme stretch. I have never heard of this guy, so if he is even renowned, it is only in the frontend JS world.
https://kentcdodds.com/discord#reasons-to-join While I personally like Discord, I have become extremely wary of people with something to sell advertising a Discord server. You see the same tactic with the crypto and NFT people, where you create what feels like an informal, fun, collaborative space, but really it is an attempt to create a self-sustaining social scene around a specific brand.
Then onto his LinkedIn (https://www.linkedin.com/in/kentcdodds/). He worked at Paypal for a while, preceded by a bunch of no names, and has some weird Google developer certification. Not really the resume of someone who can charge $600 (!) for a course in some frontend BS that will be out of date in 6 months.
His Github has a ton of activity and to his credit it does look to actually largely be "real" and not just gamifying LOC/# of commit metrics.
This guy may well be a react/frontend expert, or at least competent in the space, but this website is just a grift targeting inexperienced engineers.