I'm surprised about Jansen. He has has some poorer periods, but overall, AZ has done pretty well. I never see them though, and don't see their tactics analysed much either, so it's well possible that it's not the genius of Jansen at work here. But it sounds a little odd; I mean, there's no way AZ's squad is on the level of the big three. (I assume not on Feyenoord's either, but then Slot is obviously the best Eredivisie coach by far, so he'll make anything work anyway.)
Sounds like you're just being very grateful for having had to chance to see Slot at your club and get two years of good play, impressive results, and a title! Nice attitude.
I'm quite curious how far he can go actually.
I just hope he picks the right club; not a Chelsea-like circus. Dortmund might be a good option as well, but then they're not firing Terzic now.
Same for Kökcü btw. Hope he goes somewhere that allows him to develop further, not rot on the bench after the proverbial difficult start.