You need to decide what "successful" means. Depending on your talent on the bike and talent in self-coaching, getting to Cat 1 is certainly reasonable, but at some point, the right coach will improve anybody.

You have to consider if you have room and motivation for another hobby, which is coaching. It's a hobby on its own, and in the first six months or so, it requires a lot of time from learning and analysis. You have to be able to put on your coaching hat and look at yourself objectively as an athlete. Separate the two.

Get a power meter, some good software (or write your own/use excel), read everything you can. Learn about strategy, and guide your athlete side to take risks with attacks at different times. Really learn the sport. Each category is raced differently, and should be analyzed differently.

I made it to Cat 2 self-coached on 8 hours/week of training, but with a lot of communication with my friends over in the 33. I've lost a lot of weekly training time and requested a downgrade because of the associated loss of fitness, but my coaching hobby is strong enough to keep my racing hobby alive and competitive.

So, was I successful? Well, I wanted to get to Cat 2. It happened at age 38, but nothing wrong with that. A little late for any hopes of going further