Depends what you want to find out on you tube, simply searching 'dressage lesson' is a good place to start substitute dressage for sj if thats more your thing. Its nice for inspiration between lessons.
Is this what they have told you or what you have assumed? If it is the former then that is rather unprofessional and they should be working to adapt to the client demand!
A good coach will adapt to the partnership they are working with, they may have a knowledge gap which they will need to fill through discussion with other parties (for example I was asked to compete a Dales pony recently. Although I am fairly well versed in showing, M&Ms are not my speciality and Dales even less so. Therefore I went out and asked what the specifics were!) but they should be able to teach a variety of horses and ponies.
Do not assume that those with the best competition results or those who shout the loudest are the best instructors (or vice versa for that matter!). As around for opinion on coaching styles and coaching results!
This absolutely, a good coach will work to get the best out of what is put in front of them, I was very nervous when I first approached my instructor about lessons but I was stuck and needed some serious help. I'm an adult on a 13.2hh fell and my instructor has a range of clients from me to a member of the junior gb squad and everything between. She is approachable and fantastic with my pony. I try and have lessons every 3ish weeks and my instructor understands this and aims to make sure I have built up a range of exercises over the last year to deal with various challenges the pony throws at us. I'm lucky as pony has also been for the odd week's schooling too when I'm away with work.
