I don't mind Star Trek Generations but they were utter fools to kill Kirk off it has to be said. Could have still been part of the adventures for some years after that I reckon.
Star Trek went completely off the rails since First Contact. Such a shame.
Then again maybe they saved Shatner quite a bit from NOT being part of the awful Star Trek things we have had to endure since the 90s I guess.
I'm sure they could have found a way to bring him back if it was on the cards. He probably had other things to be doing.
I think he wanted to still be part of it for some time after. He wrote some books. I remember reading one that had him/Kirk fighting the Borg alongside Picard I'm sure. Like you said he found a way to bring his character back. Can't remember the story that well but I think it was a trilogy of books after Kirk died.
Then went onto Tekwar books, there was a terrible PC game based on that I played and then other stuff.