The vibration / haptic feedback is a lot weaker after the latest update (11.89)

Possibly but I find it ok. 

Same here. please Garmin bring it back. or add an option (slider) to adjust Haptic response and vibration

Unfortunately I'm finding the vibration alarm is unusable on the Fenix 8 for me. I've slept through alarms multiple times and I'm considering returning it at this point. I was on 11.89 and now 11.90 and it's still an issue.

No, not just you. Me too. I have just switched from latest Epix Pro 51 mm to Fenix 8 51 mm and vibrations are considerable weaker, which is a huge problem for me. And nobody cares ...

Garmin has limited the strength of the vibration motor. However, you can test its strength when you set an alarm or timer and scroll through the numbers with your finger. Then you will feel that the haptic motor is very strong. The problem is that everywhere else its strength is unfortunately limited and Garmin does not give us the opportunity to control its strength 100%. Because Garmin always works with all the problems and does not listen to its customers. So try writing to Garmin support, the more people write, the more they may start to see it as something that needs to be changed.

You can't change the strength on an alarm,it's either on or off.