Just a 'temporary boredom as a child is/was pretty normal' datapoint, I remember sometimes falling asleep at the table in the restaurant out of sheer boredom while the adults finished chatting. I don't harbour any resentment for that, and I completely understand that they needed to hang out once in a while.
yes, but i needs to be boredom in an environment/situation where they can do something about it. being forced to sit still and be quiet in a foreign house while the adults have fun is not it.
I mean, as much as the modern world wants to convince you to revolve your life around making your kid comfortable at every moment of the day, this is actually a super important life skill and you need your kid to develop it.