Absolutely correct. On all points.

I disagree. AI should be able to win. The better the AI, the more interesting the game. Ideally the replacement AI skill would be related to the ELO of the player who left

Yes, it does seem like a bug. I had one of the admins tell me that you won't see an offer if you don't have any resources, but there have been several times that I have had resources, even the ones they trade amongst themselves, and don't get an offer - not that they would actually accept it if I did see it and agree to the offer.

I was just kicked out of 3 games in a row. I don't have an issue with my internet connection. I know this because I'm constantly connected to another server for work. I tried to play, while taking a break, in the seafarers tournament and it's impossible. No wonder the other two games I did play earlier had one player exit. It can't be this common - there is clearly something wrong with the catan servers. I was also like you -- got destroyed by AI in a game someone apparently left, but I suspect that they are not "leaving" on their own now...

@Stroom Perhaps i am not using the correct terminology...but I played against the computer, exclusively during my many years on the PlayCatan website.