I think the Jax suicide at the end made perfect sense.
You have a character who tried to 'do the right thing' for most of the series. Wanting to set the MC on the legit course away from crime and honor his father's wishes. Not only was the series about how he couldn't accomplish this because of the circumstances but some pretty nasty things happened to him. Eventually, you have to figure there is a breaking point. On top of this was his desire for his kids to not follow his footsteps.
Now, I obviously don't have to make this choice but there is no way I could give up my kids and still live. That alone would be enough for me to kill myself. And in a way, that was a sacrificial love in killing himself to free his kids to a better life without the baggage of him. And the suicide would not have to be that hard of a decision because of all the terrible things he had been through and done but also for the fact that he knew he was going to otherwise meet Mr. Mayhem AND he could clean up the mess the club was in.
How does it not make sense?