I understand your last paragraph. I freelance. I started out working for an agency that promised great things. But the office politics, the working constraints soon palled and while music was a wonderful hobby, it turned out to be an awful profession - in that field at least.
I suppose I get some satisfaction now because I can choose what I pick up to an extent. I can also exercise creativity which will get me almost nowhere financially but there's time to do it. However, work sometimes dries up. Thankfully I'm adaptable enough to take up anything that pays something toward my survival!
In one respect, you're in a wonderful position: hopefully you pull in enough money to get by and you can look on it as income to finance what at the moment is your hobby, writing and illustrating.
I think lockdown is depressing us all... So I can understand how the difficulties of making a start - getting published - is amplified. It's going to be hard.
But you certainly aren't as you describe: a dead weight to society. Under non-lockdown circumstances you'd be doing a useful job, in contact with people, exercising your imagination in your creativity in your spare time.
Be brave. This lockdown can't go on forever...well, if it does we might as well all give up. But it won't. Meantime, work on your portfolio.
As others have said here, we aren't truly free and as individuals in society we have to "do what Romans do" or find ourselves ostracised. So...existentialism only works to a certain extent.
All the best...
