My dad was a plumber and I’m preparing to pass the certification that permits me to work on home electrics. They are, to be blunt, easy. An average person can pick up most of it in a couple of months. Electrics and gas plumbing carry a certification requirement because an error can kill someone, but it’s easier than passing a driving test.
Obviously, there are higher tiers of those trades that require a lot more training, but even those aren’t really comparable to the level of knowledge and study needed to become a qualified doctor, let alone a consultant.
In the UK, shortages of tradespeople are less to do with the difficulty of training, or lack of course capacity, and more to do with people really just not wanting to do the job, for various reasons.