Boring job, no imporvement, no motivation, but very high paid, is this a good reason to leave?

You should clearly define why you have NO motivation: the wrong job, wrong company, wrong team, etc.. But in many case, its the person who are confusing on what they want, having no clear direction of where they want to head to.. so they end up having no motivation to work.

My advice for you is if the reason is external, i.e outside of you like the working environment, the team, the job itself, then changing the environment, the job and the team may help. But please be honest, if the reason is internal (i.e. coming from inside you), then the ONLY way is to change yourself. No matter where you move to, if you don't fix the root cause of the problem, the problem will follow you, just masked in different format.

Good luck and believe that there will always be great places to work for each of us!