Immune phases are not fun.

Anyone else feels like that?

Most of my boss fight are like 75% immune phase or longer.
Somehow it feels frustrating. First I wait for the intro, then I do few seconds damage and have to watch another animation going into the immune phase, run around, wait for the next animation going into damage phase, do few seconds damage and back to waiting.

It is kind of over tuned, the boss fight feel like waiting instead of fighting.

oh, it is stupid as hell. One reason Elder Guardians are so darn annoying in PoE 1 is because of the small cut scenes we are forced to watch EVERY TIME. But it's been like this for years and GGG hasn't done anything to make the experience better, so they most likely never will

Invul phase is a sign of lazy game designer.
If you can't design a boss that is challenging yet fair using regular mechanics, then you can always slap invulnerability on it and call it a day.