I'd like to direct your attention to this reddit thread where the commenter describes a system for training DPS players for strikes and raids; the relevant section is copied below.
Idk if this is elitist or not but maybe there should be some incentive weekly/daily to hit at least ~20kdps on golems in the golem dps room. And maybe more rewards (bronze, silver, gold) the higher your benchmark.
It seems a large part of the high barrier to entry with raids is around the lack of any kind of training system (like fractals have with T1-2 fractals) and Strikes don't really address this since they can be carried by a small number of players and there is no feedback to under performing players. Having some kind of adventure to test/train players could make a huge difference in the average ability. There could be different adventures for DPS, boon support, CC, and healers. I've outlined some ideas but I'd love input
Have a boss with a significant amount of health but minimal mechanics. Maybe it moves a few hundred units or has some weak attack but otherwise mostly stands and takes it. Then bronze could be beating it in a time equivalent to 5k DPS, this is low enough to be achievable for most players and to inspire them to push for higher levels. Then silver is at ~10k-15k DPS, and gold at 20k-25k dps. All of these are achievable for any DPS build, and many boon support builds, and if the rewards are good enough (or unique) could encourage players to learn how to dps better. There could even be higher tier bosses with dps checks in the 30k+ range for the hardcore players. Adding some kind of feedback or advice in game could be helpful too, ie "you did X dps and need to improve Y amount for the next reward" or "checkout this websites for better builds".
Have a boss that the player can't damage and instead has to heal and support NPC's that use some kind of fixed attack. Boon support players then have to buff the NPC's to increase their time. Similar logic to the DPS adventure above for reward thresholds.
Similar to boon support adventure except you have to keep the NPC's alive. Either until they kill the boss or as long as possible. Due to how classes are constructed in GW2 this might get lumped in with the boon support adventure.
This one would probably be similar to the DPS adventure with either a single boss who couldn't be damaged until the CC bar was broken or multiple adds with the same trait. This one would probably have the most difference between classes as their CC toolboxes differ significantly but there could be different thresholds depending on your class in addition to an overall leader board.
Adding titles to the adventures could also remove part of the need for KP. I.e. if I'm playing DPS and I show up to a raid with the "This dps player can do at least 25k dps" title then at least the commander knows I'm reasonably competent, even if I'm inexperienced for raids. This would probably require making the titles character/class specific, though that could be accomplished through having multiple achievements.