If none of them is pinging you at times to see if you're available, you were probably an unremarkable professional or you have extraordinarily bad luck.
It's not a bad thing to be average or mediocre, it's what most of us are, with a very small percentage of great professionals in a classical gaussian distribution.
But people that impressed their former colleagues have queues of jobs lining for them. And that's where most of your focus should go if you want to have a career.
Most (normal) people would cringe at the thought of spending 8 hours straight, alone in your office, to fix a bug or write some new code; but we thrive on it.
Still, even introverts need human interaction on occasion. Networking is important, even if you are just interacting with others like yourself (with the same apprehensions).
If you find it extremely uncomfortable to socialize at all; you have to work at it, even if it feels unnatural. Like many things in life, the more you do it, the easier it becomes.
Most introverts I know don't enjoy being around people all the time, but still build and maintain meaningful relationships with a small number of people close to them.
If you do want to be better at this, but you're finding it difficult, have you considered therapy? A good therapist can help you feel more confident in building relationships, so you don't feel as drained by them, and give you a safe space to learn and practice those skills.
Ultimately, though, I ponder about your professional connection problem. You don't need to be super close friends to have people refer you for things. Just pleasant. I see what you say, but part of your career as you advance is managing people's feelings. If people don't walk away feeling good from interactions with you, then I don't think you're doing your job well. That doesn't mean you have to smiley and be fake, but people can't feel like you don't care at all about what they are emotionally invested in whether that be the project or their career or whatever. It's worth considering that you might be lacking a skill for higher levels of work and even if you got those positions you'd hate them because of how much emotional labor is involved.
I'm no longer happy with my current position since they stopped remote work, and I've been looking for other opportunities as a java developer. I've applied to at least 30 positions so far and NONE have responded back....
Have you thought about a career coach or hitting up a recruiter at a recruiting company? They can 'advertise' and promote you to their clients. Often times they only staff temporary positions (i.e. v-endortrash), but sometimes it is permanent placement.
Making Peace with Personal Branding: https://www.fast.ai/posts/2017-12-18-personal-brand.html
Your blog would detail some of your work experiences you wish to write about, such as tutorials, case studies, etc. I realize it's likely a longer game than classic networking.
How do you define that?
Posting on linkedin?
Going to events?
I come to this realization too. The world is not a meritocracy like we are taught as children.
In my case, I have a disability that makes networking difficult and feel immoral to me. Frankly, any company spouting DEI and still supporting networking is hypocritical.
Every single one of my jobs came not from networking, but just cold applying to positions. If networking feels inauthentic to you, I would say just to forget about it and work at getting good at your craft. If you can demonstrate you have the skills and a company has a need for that skillset, they will hire and networking skills will be irrelevant.
Also, if you're not having much success at applying for a type of position, it may be that the timing is just not right, e.g. a company has a superabundance of web developers, but what they are really in need of is embedded software developers. In a lot of cases, it's not about you, but about what the company's needs are.
At one point in time, I applied to a company and failed to get in, but later on, I tried again, got the position, and it was a great opportunity. Was I that much better? Not really, just a timing thing.
So don't give up and keep moving forward with practicing your skills and applying. The more you prepare and try, the better the odds of success.