While maybe I've played different games, I've seen-multiple times-games where players have said "Gear score xx+ req", whether it be for a raid, guild, group, whatever, it's happened.
I mean... yeah, stuff like that can happen.
Now that you say it, i do remember requirements like this from the old days in WoW, but (in my experience) these requirements were never irrational and were not even held up, when it came to skilled players.
As long as it is kept reasonable, i do not see a problem with it.
I think the goal is to try to avoid this. I don't think we need gear scores.
I understand why some people do not like this, but there is a good reason for implementing scores as well.
If there is a significant power difference, depending on equipment, that is.
In games, where there is group/raid content, the group has to be set up in a way that allows the collective to succeed.
The leader has to think about who should get an invite.
Looking at equipment (in games, such as WoW) is pretty much the only way to get some estimation about the player's effectiveness, without knowing about their personal skill.
If a damage dealer is required to deal 6k dps, which is usually achieved with 4k gs, then a person with 2,5k gs will probably not reach that number.
A player who can deal 6k dps will still get invited, even if the gs is lower than expected.
Gear score was not the reason for people not to get invited, but their (estimated) capability of doing their job.
People might not get invited, because they are less effective than others.
They get pissed, because the success of the group is valued higher than their happiness about being allowed to join.
In the end, there will always be a way for people to rate players, based on objective things (subjective influence not included).
Having something like gear score just makes it easier.
Since Ember is not supposed to have instances, i guess, even if there was gear score, there would not really be any circumstances, where anyone could be "penalized" for having a score that is "too low".