Good points overall. Depending on the company and the team there could be several other factors too that could lead to boredom.
I think one of the biggest factor could also be lack of freedom and trust in the team which could easily lead to boredom and frustration. Morale events tends to keep the team together.
Being a PM (substitute any role here), I have experienced that, if I as a PM do not do a good job of articulating why we are doing what we are doing and jot down the requirements, it sends the team into circles which results in boredom as the team do not see success. So, being a good team player is absolutely necessary to keep your team happy and away from boredom.