If you don’t know what you don’t know, and you have confidence in your own judgment and ability how do you know when specialist help is required? How do you know if the job or task beyond your abilities?
When it comes to plants every man with a dog and retired lady who makes tea has a ‘how to’ on pruning; some of these are good, some of these are not that bad but most are just wrong!
I had been planting trees and shrubs for over 20 years and I didn’t realise that poor planting was such a problem - but clearly, it was then and it seems that it still is.