There is not a flaw in the design. That would be like saying there was a flaw in merits because the best way to get them at 75 was in a party. It does not matter how long you have been on and what you have seen. I am telling you I have made, joined, and done these parties, and there is also nothing stopping you from doing it yourself.
You can say anything you like, and I wouldn't worry about taking it personally. However, I think it is likely others feel the same as I about sorts of things in this game. While it may not pertain to job points. Many players if you recall were very upset the REMs they worked on and were a little proud of. Were suddenly insignificant compared to delve weapons until they were updated again. So I do think that there are people who either proud (or at least happy) of certain accomplishments and capping job points would be one.
Then there is this ridiculous impatient "gimme gimme" crowd who wants it at their speed and when that speed is quick or instant gratification they then turn around and cry for content.
If you are struggling for everything perhaps you should look at your job and what you are ready for. I can clear a yorcia delve 1-5 with 20 minutes left with a complete PUG composed of two Tsumarru SAMs who have Fudo and accuracy gear for the T4, a 3 song eminent flute BRD, any reliable WHM, a SCH who can nuke, and my COR/dnc. In the same gesture I can make a PUG with five of the same people and a new SAM in 119 tsu who costs us the run because they simply are not ready.
Same for difficult celestial nexus. I have made over 10 different PUGs for it with RNGs who have skirmish bow, and only lost a single time due to a bad WHM who layed on the floor most of the fight. Half of this game is knowing and then 25% is skill and 25% is gear. I assure you the only barriers in this game are the people you are with and what everyone knows.
Finally, job points are not merits, and we have already had large scale merit increases. You can not look at them like merits. They were simply put in the game because we needed something to give us a reason to XP when merits are all capped easily. KIs are only as good as the ammount of things you need from them, and that is faster than job points.