As someone who, on occasion in the past, also feels like they’ve sent SOS messages of loneliness on an isolated island as a hurricane roars overhead, I sympathize with your feelings of isolation and a lack of feeling appreciated, @Reforged.
My POV with regards to that is aimed at people who claim to be my friend, but always fall short when it comes to actually being my friend.
To them and them alone, I say the following:
You claim you’re my friend.
Yet, when I try to have a levelheaded evaluation of our friendship due to your actions and seeming lack of interest in our “friendship”, you get upset, think I’m being emotionally manipulative and walk away like an impetuous child, rather than engaging in a healthy, civil discussion with someone who has, time and again, proven their friendship to you many, many times over.
I’m extraordinarily selective in who I befriend and truly open up to, and its the actions, or lack thereof to be precise, of so-called “friends” that are precisely why I lock myself off to all but those who actually are my friends and show it through their actions.
Talk is cheap, actions count. If you can’t be bothered to be an actual friend, and, when I politely bring up the matter because I truly care about our friendship and want it to succeed, you huff and puff and act like I’m at fault, then it begins to become blindingly obvious that maybe we just weren’t the friends I hoped we were, thought we were and you claimed we were.
I’ve got bigger fish to fry in life, so if you’re not willing to actually be the friend you claim to be, or at least engage in an adult and respectful conversation on how we can fix things, then let’s just amicably go our seperate ways and be done with the whole thing, because its obvious only one of us is truly putting effort into the friendship.
Whew! That felt good! 
Anyway…
@Reforged The best advice I can offer is to just keep on doing the best you can, no matter what others say or how they act.
I know that that’s far, far easier said than done.
I’ve had my bouts of brooding in years past where I’ve thought “Why can’t I seem to connect with others?”.
I think it over, think of where I may have made mistakes and then use that as a basis for learning new things from, so as to hopefully engage with other like-minded people in the future.
No matter how lonely and isolated I’ve felt in the past, I keep my chin up, maintain a good sense of humor (which has been scientifically proven to be a healthy attribute to have), shrug off the weight of people who didn’t know what they had in me as a friend and strive toward a better tomorrow as best I can, because I truly and emphatically do believe that I will eventually befriend people who do see the friend they have in me and who, through their actions, show that they truly care as much about our friendship as I do.
Its going to take time. Its going to take standing tall when you’d rather collapse. Its going to take mustering up all of your optimism and say “I know things will, sooner or later, work out for the best and I’ll make some great friends.” when you’d sooner tell the world to go screw itself, but you cannot give up and receed further into the shadows of isolation, because that solves absolutely nothing.
Hard as it may be and clichéd as it may sound, you have to keep putting one foot in front of the other, do your best to be positive and focus on what makes you happy, because you will meet people of like minds who do get and appreciate you. There are things in life we sometimes have to wait a very long time for, but as the saying goes, “It was worth the wait.”
Anyway…I hope that ramble can be of help in some way. 
Maintain the course, do everything you can to the best of your ability and you will get off that figurative island and into a group of people who do cherish you and completely see you for the wonderful person you are.
Awe, don’t say that my friend.
