Pretty sure the answer to this was said a page or two ago. To check to see if you are skilled enough to clear it and be ready for the next fight. If a player isn't skilled enough to clear the gatekeeper, then they have no business whatsoever going into the last fight. Currently, V11N is a great gatekeeper. If, after a few pulls and learning the mechanics, you are not skilled enough to deal with Larboard/Starboard, dealing with the Duty Action, and dropping your puddles while avoiding Flamethrower or a Rocket Punch, then you need to work on that, and generally have no business touching higher skill tiers, which would be Savage.
Gonna add this in, even though I hit my post limit. If a player cannot comfortably dodge larboard/starboard, dies to it in conditions where the boss isn't being moved around, and then tell themselves that they are good enough to move on to a stronger fight, then that player is a detriment to their party, and likely candidates to be carried. Players are still getting killed by that mechanic, even with reminders being sent. Players are still getting hit by the rocket punch. Players who have run this fight multiple times, and still are not able to avoid dying in good conditions - dying due to their own failure to successfully complete mechanics.
The point is not to survive - the point is that if, in good conditions, you cannot stop dying to things like this, then you as a player (not you in particular Riyah) are a problem if you move into Savage with comfort that you survived. You've seen some of the threads - some players can't avoid dying to it, even with the solutions being explained to them (associate Larboard with boss attacking its left side). I wasn't here for HW's launches, but I was definitely here when Shinryu mopped the floor with complacent players. I was here when Tsuku stepped on some players who were used to being carried. You can't say gatekeepers will be stronger than that, when you have a history of not wanting harder content in the game.