Some will always blame the wrong thing. If you have a complete lack of experience in Mythic plus a leader is not going to pick you over someone who has better experience. This is the same across the board in all PuG content.
It is not the fault of the addon. Anyone can build a score if they want to, if they don’t to then that is their choice. The score is only experience translated into a number. It is no different to looking at the armory, except it is much more detailed and doesn’t just show your highest run like the armory does.
If Raider IO was banned tomorrow those people still wouldn’t pick the people they rejected for their groups but we would all be checking armory instead which only shows the best timed key and nothing else.