What if I am really not that good?
Read a few guides on how to write. When you get to the point of thinking, "this one has nothing new", you've read enough. Make succinct notes on the X-not-Y points they make. (You'd be amazed how few there are in whole books on this subject, partly because it takes a lot of text to explain, defend and exemplify a point.) Then read your old, recent and intermediate work with an eye to whether you've done what you're "supposed" to. This will help, but I need to explain why.
Now the "rules" aren't perfect or ironclad (great authors often find contexts they should rightly be circumvented), and at least one book argued they're not rules at all, just "observations". Don't worry about that: reading the same basic ideas in multiple places gets your mental Is dotted and Ts crossed as to the nuances, and for now the aim isn't even to assess your work by the rules anyway. But you'll discover you can self-critique with much more objective insight than you probably expected. It'll give you humility; it'll give you pride from your progress; it'll give you ideas for revision; it'll help you write better first drafts, or at least better second ones, for your next story.
I'm a writer, but I'm also a programmer. Both disciplines have any amount of writing advice, and any number of people who dispute it, and you will form opinions about it all. Seriously, that's a good thing. When you can articulate why what you did makes sense from certain perspectives, and why sometimes you did something different and think you know why it was prudent, it'll give you the feeling of self-empowerment.
But what if you're really not that good? The only meaning of "good" I know in this context is having the effect you meant to. If you're really not that good in that sense, you'll notice when you do the above. 487
But remember: "not that good" really means "not that good yet". The right mindset, one of understanding writing rather than just trying it, doesn't mean you have to "agree" with everyone else; but it'll help you know what personal progress looks like.
What if I am wasting my time my family's patience on nothing?... Almost each and every beta reader (not personal acquaintance) told me I am good. But how would I really know if I am any good?
Do your beta readers include your family? Oh, it doesn't matter. The trick to knowing whether feedback is helpful is whether they've gone into specifics. There are some online guides in how to beta-read well, and how to brief beta readers on what kind of feedback you need. "This was good" is useless. Ideally feedback on a novel should be a few thousand words, most of it critical, but with some examples given of what worked well too.
I cannot stop writing.
Good. That's arguably the only good reason to write. All aims to achieve specific things by writing have the downside that their odds are too poor to make them good reasons. (That doesn't make the aims themselves bad, though.)
If I have this right to ask unknown people to spend some hours of their lives with my books?
Have you tried trading critiquing duties with other writers? Mutual beta readers, or "critique partners", are a wonderful thing. All the feedback you receive is not only earned, but from a fellow writer's perspective (which theoretically makes it more insightful - I've certainly found it gets more detailed); you get that "we're all in this together" feeling all writers deserve; seeing someone else's writing, and thinking about how their thought processes compare to yours, can help you rethink what you're up to; and you get to read a free book. 487