I've only just came back to the game after 3yrs but I can clearly see the problem after doing Coil and Alexander Savage, the problem is "randomers"
It's better to spend a lot of time to get a group together and make a static so that everyone is used to each other, it's a lot more fun this way and you will make friends in doing so as well.
I've completed these "hard contents" with some with skilled players and some with new players who were never really confident in their skills in a MMO, most were new but if you point out what they were doing wrong and if they learn from doing it your team will improve and eventually clear the content, you really can't do that with random players as it's always the same result... They do not care... :/ it's about consistency in the group, tanks need a partnership so they know which roles they are doing during mechanics, healers also need to know how each other heals etc if everyone is the same every time then it makes things easier.
I also usually find that most players at endgame are elitists and are some of the worst players to meet in the game, you wipe or if anyone makes a mistake, they start to whine/cry and go full toxic mode, you also can't really tell them anything because they already think they are better than you and know everything already so they don't want to listen to you... you are going to meet lots of these types of players if you are doing it with random players. This never happens if you have a static and usually if they are new they are more willing to learn from you and they don't mind wiping.
My suggestion would be either spend some time and find players who want to do the same clears as you to create a static or make sure you put in PF "not to leave after a wipe" or tell each member when they join the party what you expect from them etc, if they know in advance then they are on the same page as you.
I'll be looking to get a group together for a static soon and while it might take a few weeks to get a group sorted it's also a good time where you can get a group ready for the new expansion as well.