I hope I can give you some hope from another guy who felt pretty down in his mid 20's too.
First, here's the deal: all those 50's songs and teenage love movies are fantasies. Love exists, it's powerful and worth pursuing, but using them as a template is like reading the Hobbit to learn to make money. Fantasy is vital to the human experience, I'm not knocking it, but we have to act in reality. My story is nothing like those songs or movies, but it's turned out to be a happy one. I obviously can't give you all the answers, but I can share the path I took:
At your age I hadn't had much more success in love than you. I didn't hit my stride romantically until a couple of years later. The rough advice to work on yourself first is good advice: try to tame your anxieties--we all have them, settle into your career, get into shape, find your style, and most importantly find passions. You don't do these things to find love, you do them for yourself. It seems a bit backwards, but when you are happier with yourself people are happier with you. That happiness can grow into other things. The good news is it's not as hard or as long a process as it sounds, you just need to start some inertia, and as long as you are moving in a positive direction you and those around you will view your positively.
Now that we have some positive energy around us the next step was just to meet people and get to know them. I stayed off dating apps--those just encourage the worst behavior in people. I just made it a point when I went somewhere to talk to a new person or two--this was where my anxiety lived. Hobby related courses, social events put together by friends, church, club meetings, where ever. I was already going to all these things as part of step one. If the conversation with a woman was lively and she was interesting I'd ask if she'd like to get coffee or something low key. Just to get to know each other, candidly talking about my dreams, desires, hobbies, beliefs. This is the most important part don't hide or try to present a puffed of version of yourself and just focus on getting to know the person across the table. You are trying to find someone you are compatible with.
This went on about two years. During this time I got told no a lot. I made new friends I still get along with today. I had follow up dates, then I got ghosted. The whole spectrum. When you communicate in this no expectations, honest, candid, and platonic kind of way your relationships form or die pretty naturally and relatively painlessly. I was looking to get to know people, not look for the "spark". During this whole period I never had a "real girlfriend" despite apparently--according to a friend--gaining the reputation of somewhat of a ladies man. I find this especially funny as I wasn't hooking up with any of these women or anything, just getting to know them. I was looking for someone who shared enough with me to become my wife.
When I met my wife she told me flat out she had no interest in dating me, but was happy to be friends. I told her that was fine, but I didn't take that changing someday off the table as we didn't really know each other well--open and candid. I just became her friend, no ulterior motives, no secret pining, no huge romantic gestures to "change her mind". We simply grew closer as friends, helped each other out, spent time with each other. In time, I thought we could work as a couple and told her, she didn't reciprocate. But, we could, and did, continue as friends. As time went on we spent more and more of it together, and I became the first person she thought of. Then we started "dating."
Now is where all the romantic gestures, letters, sparks, and so on begin. Not in the beginning but the end. Really, they keep going--that's important love is a verb not an adjective--you have to choose to keep being romantic and in love. Back to the story, we went fast from there: since we already knew each other so well from the friend phase we spent less time officially dating and then engaged then we did as friends. Less than a year after becoming a couple we were married. We've been married a decade now.
TL;DR
That was a lot, in short: become happy with yourself, and others will be happy with you; don't look for a storybook "spark", but candidly and platonically get to know people; let a romantic relationship grow from there; then let the romance flow.
Ironically enough, the reason why I want myself a wife is because I'm sick to death of putting up with people who...have betrayed my trust and abandoned me again and again...
I want to get to know people, but the last time I did, they hurt me in more ways than you can imagine, traumatized me...
So the reason I want a girlfriend is for practice, so someone out there can help me overcome this social anxiety of mine.