What about the people that are new to the raid, or rather, just new players in general? I think most people are willing to learn the raid's mechanics given the opportunity. Do they just stay dead for the rest of the raid until the next one they do? How can you practice something when someone expects you to be perfect at it your first few times? You have the assumption that a lot of people just don't try when they're raiding, that they just run at the boss and try to do their smashes/moves and expect to be revived after they die without even trying to dodge or block and that's just not true.
Everyone makes mistakes. We're not all perfect. Your argument that we have merc-like pots now and it should be impossible to die is just another excuse that's basically saying get better and stop being bad. True, it's a lot easier now since you get "better" armor and all but that doesn't mean new players deserve to not get revived because they've never done regina before and got hit by a 4k dmg red attack or got swooped up by her ohko that they've never seen before.