Was Y!A doomed or could it have been stuck around longer if it was updated properly? ?

I think inconsistent moderation was a problem. Yahoo needed to either moderate all comments equally or only moderate comments that were illegal. The removal of the appeals system was a reporter troll's paradise

Also getting rid of the comments was a mistake, the site had evolved into a question based chat room, there was an appeal to this and it should have been continued.

The Anon feature was a disaster, significantly increased bullying and was not needed where all were anonymous anyway.

For those who want to join a few of us have gone onto Reddit, going for very little moderation, anything goes so long as it's in the site rules

Corrupt moderation primarily led to its downfall when walls of texts from multi-account holding trouble makers could no longer be stopped. Changing from the 'Green' format was a big mistake. In these last months it is really only been the trolls who have kept the argumentative sections going and virtually everyone else reverted to posting as anonymice. Then there's the fact that Google searches have become more intuitive; so the only advantage that YA still had was the ability to tap into other people's personal practical experiences. Then to see these answers being trashed without effective punishment was just poison. The site shot itself in all four of its feet.

None of those  All they had to do was get rid of the trolls and prevent them starting new (and multiple) accounts, and to tackle retards like the tank troll. It was doomed because people seem to think freedom of speech is a licence to insult others, and all it has demonstrated is that regulation is necessary.

All of those, but primarily the people who think it’s ok to be absolutely vile, and hide behind the anonymity feature to hurl insults instead of making any attempt to answer the question. (See below.)

All of the problems could have been sorted out if there had been proper moderation of the site, but the way it was run, multiple account holders could get perfectly reasonable questions deleted whilst they got away with murder.

 In this case the old adage of everything carrying the seeds of its own destruction is true.

It's been ruined by stupid trolls like you