All I see here is complains about people being restrictive to prevent their group having too much of a problem. The lower the iLvl and experience minimum expectation, the higher the likelihood of a group having issues.
If you don't like it, you're more than welcome to run your own group using OpenRaid/oQueue/Trade Chat and run a group your own way. It's not as easy as it looks.
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When I run a group, I make the minimum around what my character is, ie. for Flex, I expect people that are 530+, but I prefer higher as I don't like being in a Flex which has an LFR situation, if I'm more than double the second place on DPS, I'm doing too much work in comparison to the other players in the group. (My toons are 550, but 530 is more than reasonable for a geared Flex group)
Likewise though, if someone is 510-520 and they want players that are 530+, they're just looking for a carry.