I'm fine with those lock outs - as already said: This content isnt really meant to be dowend in dutyfinder (and if you're complaing about how no one is doing it anymore: Back in the old days you would have build a static, you would have gathered friends around you to kill Twin because of the weeklylogout - and even without that later: I've always seen a steady amount of ppl looking for the kill or a farm in pf - it havent really changed). That goes even more for Second Coil ofc - you're meant to find some friends to kill it with you or even get carried through so you'll have acess to later fights. Specially with Coil its not only the raid. Its also a story - are you skipping chapters in books because they're to difficult to read or understand? If this is the case you may stop reading the book or come back later (or ask someone to help you understand).
That doesnt go so much for Ex-primals though - still they've already loosed the requirements (Levi was logged behind Ifrit, read: behind Titan...).

All this fights are far easier if you're doing them with a bunch of friends or at least people you know. What you're saying sounds to me like: "I've got this one wall I keep running into on my own - please make that 8 walls to run into at the same time!"

I can only speak for myself but I like to do this content with nice people that I can even call "friends" - and that sort of people will simply clear t5 (and t6, 7, 8, 9...) with someone again so they can progress together after that. I dont think that this barriers are keeping anyone from doing this content as it is intend: with a skilled group of people who kinda know each other. I dont see any real reason to change it - if you cant down the stuff thats meant to be easy you may need to learn a little more...

(And yes I got that your point is that the encounter isnt pick up group friendly - my point is that the encounter never was and never meant to be like that. And I dont think that this should change - if you dont wanna make friends in this game or at least find people to rely on in this sort of content this sort of content isnt really meant for you, I'm sorry but thats at least my point of view. I know that this might be frustrating and I do understand that but I dont want all of the content to be faceroll-speedrun-shit and that equals the need of playing in a well trained group.)