For me, it sounds like Alex had been considering leaving after season 10 when Peter was writing the finale so he planned for that, but also planned for a season 11 without Alex. But then after CBS found out that Alex didn't sign on for season 11 they decided to end anyway. That is my impression of it, but I could be completely wrong!

Exactly! how I saw it in the future for H5O Steve coming back and lead the Task Force again as leader the fighting and action was for Lincoln, Junior and Adam.
We all know that Steve went through a lot he deserve some time away to escape from it all.
I hope the show will come back some day so we can enjoy two men bickering in the Adirondack chairs looking over the ocean.

I see it like this: Alex has decided that he wants to leave after the season 10. So CBS has decided that it wants to continue the series and do season 11 without Alex. Peter Lenkov had to figure out how to do it without him. So he introduces this new character, Lincoln and Steve will leave Hawaii and Five-0. At the same time, believing that the network for a while (let's say in a few months when he rests a bit) would be able to convince Alex for a return. But later for no reason CBS changes his mind and ends the series, and the finale of the series becomes the finale of the series, because it's too late to change everything.

They should have had Kameonka and Duke on the show saying farewell. Really not fair. As also would had been nice to have a cameo by Chin, Kono, Jerry, and Max though they left a few years ago.

But really wished it was three hours not two hours as they were split one week to the next. Did not really tie up loose ends.