The cold hard facts...
Very few people (read none) care how much time you put into your bank alt turned side project let alone any of your characters... It sucks getting booted for any reason, but it's easily avoidable if you take the rest of what will be your potential group into consideration.
The reality is most people are looking for a quick fix to having to assemble a group like you remember. LFD is that solution... Press the button. Wait and go. You did it just like they did...
The issue you're running into isn't uncommon. If you're needing on random dungeon greens you likely haven't done many if any quests (the items from the refreshed zones are pretty decent) that would otherwise see you in a position to be competitive and contribute to the group in a meaningful way.
To me personally you're describing yourself as the person I loathe to be put in a group with and the primary reason I avoid queuing at all. You're putting your own shortcomings onto the shoulders of others simply because the option to do so is there and easy.
So as much as the general communities attitude is not as pleasant as it could be, you're putting yourself and others into the situation by queuing with poor items and minimal knowledge about what you're doing in your role. It isn't acceptable just because you're a "casual player" trying to have fun because you're effectively removing the fun for 4 (or more) others player casual or not.
If you want to do the dungeon with your friends who know you'll be their burden bare so be it, that's a choice they making knowingly, but inflicting yourself on the community because you can... Well you can expect them to use their choice to remove you from the group. The fact that you were allowed to stay as long as you did in the situation you described is really a testiment to the communities willingness to give you a chance.
I know it's not the opinion you likely came seeking, but if it's about casually having fun I don't see any fun in carrying strangers through content or being carried through it either.
*Edits: iFail correction(s) & Link to OP
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