Of course the thing with learning to write sitcom is there are three stages.
1. Innocence - when you simply don't know how it's done. At this stage you definitely will benefit from reading books and going to courses because they will put you with like minded others and not assume you already know the business, so formatting, scenes and beats are important. Also character and the trap of sitcom, which in a lot of ways is more important then the comedy itself. (They can always 'fix' that)
2. Skills. WHereupon you learn the various skills you need, send things out and get them rejected only you can't yet figure out why. This is because sitcom writing demands a complex skill set that is more easily covered by a pair or team of writers. gags, plotting, ideas, character, scenes - all are different abilities. It can take years to perfect these are most sitcom writers who got lucky would certainly say that they were still learning a decade into being produced. (maybe not Ricky G)
3. Experience. NOw you KNOW how to do it and it's just a matter of time before someone picks up one of your ideas. This is where the endless fight between optimism and pessimism comes in. You make contacts and learn the business. You really discover how hard it is to get 'pregnant' with a piece. Often, if you are a writer for the BBC, if you persevere for long enough they tend to give it to you by default. This is depressed but you have earned your stripes. And even once you are on telly there is no guarantee you will get on again. You simply have to stay resilient, confident about your talent and refrrain from killing your co-workers on your miserable day job. Good luck and keep at it.