I did this in retirement, was on my bucket list. Ended up teaching at the school for a few years, part time (pay covered my gas to drive to the school, for the fun of it). Gave me a reason to talk about boats in the off season with like minded people
Other than that, never exercised the certificate.
Yes, you will learn the rules of the road. You will get really good with paper charts, set and drift calculations, etc. You'll get exposure to people pursing careers in the maritime business, which is interesting. I learned a LOT from a retired coast guard master chief who was instructor. Met lots of interesting people in the trade.
If you plan on running a charter business, talk with people in the business before you start. From the people I know, it's not what you think it is. Similar to the guy who retires from Wall Street and buys an inn in Vermont because he went there once and had a good time. Guess he didn't notice that the owner was doing the laundry and cleaning the kitchen.
I'd second the recommendation for a structured course.