I'm not sure why you're buying the new watch and expecting a different outcome, the new watches use the same method of collecting heart rate data which is measuring the amount of light that is reflected back to the sensor. Your tattoos will be hampering the ability of this method.
Now - your solution(s) depend on what you're trying to achieve:
- If you're only interested in getting the watch to know that is is being worn so that it mutes notifications on your phone (for example), you might need to see if a smart ring (like the Oura ring) has that ability.
- If you're wanting to track heart rate during workouts, smart rings aren't known to be the best for this - you could look at a heart rate strap around your chest or there are probably headphones that take your heart rate from your ear. I used to have some Sony earphones that did this
Are both your arms at the wrist tattooed? Could try wearing it on the other wrist, although it's a pain accessing the buttons if you wear it on the right arm.