hi Varun,
Many tools have free ressources and guidelines online, see youtube, PluralSight, TestautomationU etc. Still you can never becomes an expert in no time, but you can read up on other peoples experiences and practices. 
consider that the people using the tool tried to their best ability and knowledge at the time to use the tool effectively. Perhaps they where novel in the use too? or didn’t have time/bandwidth to do it “correctly”. In situations like this I reflect on the Jerry Weinberg quote “Things are the way they are because they got that way” and try to forgive them.
If it’s not important enough leave it (consider: Should we just delete it). at least as a refelection that since 2019 these tests have not been important enough to wrap up. Also consider if an audit came by and asked - why did you now update these
ADO is just a tool - and it promotes one way of organising your tests and things. Work with ADO as a team to establish how you make it yours - balancing what ADO provides and what you want as a team.
Besides that I’m no ADO expert - others might be for a deep dive.