As far as people inviting you, you can ask anyone on the X1, I will join into games all the time and most of the time, im welcome to stay. If not, then I find another party to join. That is why there is a join option. If it is that much of an issue to join someone for you, then send a msg to members, "Hey, mind if I join?"
I explained what you needed to do to get better gear in Destiny, it isnt anyones fault you dont want to heed someones advice. This isnt the 1st time either that someone has tried to help you and you did not take the advice. Its just how you are, you are set in your ways. The raid is something noone wants to bring someone less than 26-27 into, and its not saying that person is a bad player, it is because at lower levels, you do less damage and in the raid, you need to have all the damage output you can get. Also, if ur gonna help someone level up, it is best to do it with the highest lvl character you have. This way, the missions can get done faster.
Warframe is a different type of game, which you always need coordination within teammates and with the amount of time I can game, left me with always trying to find someone to play with as well. I got tired of it so when Destiny came out, thats what I went to.
Play was always Galacticas friend as far as I know, so for him to go to Galacticas clan is fine. We have had members that felt we didnt fulfill their need for competetive play which is also fine for members to pursue.
I think what you need to do is just take a step back and evaluate. Because what you told me 3 days ago now, is that you decided not to completely leave the clan and now yesterday you decide ur done. You are welcome to do what you want to do. That is up to you.