You're mixing issues a bit.

If your current work is, as they say, "soul crushing"... you should invest some of your personal time to leaving that job. This is an independent decision of what you want to do/should do afterward: yes, you can quit/work on your own stuff.... but there are other possibly good outcomes that include the "quit" part, but something other than bootstrapping a business.

As for starting your own business, I found it hard to bootstrap something meaningful without being full time on it... so that part of what you're talking about does make sense. But you need to be ready to burn cash for an extended period, consider: 1) how long it will take to get your product/service into something making reliable income (meaning enough to cover business expenses, your expenses, as well as enough to bank some cash so that you can ride out the hard times); 2) if things don't work out, you still will need cash to burn while you look for new employment... or more seriously risk having to take the first thing that comes along and being, perhaps, in a worse position than you are now. Not having dependents is helpful, but you have your own needs that, no matter how meager, must be accounted for.

I did the bootstrapping thing myself, but I was lucky in a sense. I had run out of runway cash and had to take a job quick: the job I took saw my bootstrapping effort as a plus, and after I was there for a few years, I was allowed to moonlight on my original business to get it stable... and later when I left that firm, they were a client for while. (my business has been self-sustaining for about 7 years now) Don't count on that kind of luck, though, and to that point. If you don't have the cash (or access to it)... get out of your current job, but almost certainly get another.

As for people's / family's opinion: meh... you need to have sufficient confidence and independence to pull off a bootstrapping project. If you second-hand your self-worth to the opinions of others: then you need to question how successful you are likely to be. Much of being an entrepreneur of any type is being able to see opportunities that others don't. If you rely on the opinion of others... well, you may see a contradiction in goals. None of this isn't to say that well qualified or well reasoned opinions shouldn't be listened to or taken seriously: they can give valuable perspective... but fearing those opinions in determining if your vision is legitimately right or wrong is probably going to put you on the wrong path. The only valid fear that comes to mind is if you intend to use those people/family as a safety net if you fail.... I would suggest planning and preparing so that you don't need to call in help should you fall.

Also, be aware that your business will take a life of its own. I was able to bootstrap and get stable because I did smaller consulting gigs across a lot of long term clients, but ultimately I wanted to build products. Well, great... now I have a good cash flow as my client base come to me with new projects and I have "hard times" buffer, but I have so many client obligations that I have trouble getting to product building part... which really needs to be full time. There are solutions to this, but they are not easy to pull off at my scale... I do well, but not so well as to staff up, for example.