Can contribute a bit here-
Would suggest there are two distinct motivations that should be teased apart. One of them is self-worth, one of them is skill/expertise development.
Self-worth: just about all of the folks I know who don't have a BS and are working in tech feel like they are imposturing. The absence of a credential impacts their personal sense of self-worth and qualification. A number of these folks are very, very senior, extremely skilled, well respected, etc. From what I have seen, it does not and has not impacted their career development/potential in the areas where they have skills. The imposturing is purely in their minds. I relatedly see folks who have a PhD from a second or third tier school and have a self-perception of being failures. In reality are incredibly sharp, organized, competent- ideal colleagues. Your mental health and self-image is your own, but this is a vote not to spend time/money for a credential primarily for a sense of worth.
Expertise: this is a different dimension. The areas you mention- some kinds of ML, 3d graphics, distributed systems, many others- to work there day to day requires deep and specific expertise. It does NOT require a degree. Just skills.
To learn deep things, you need to do deep work. There is no other way. You need to carve out the time and brainspace to devote serious attention. An academic environment with guidance from faculty following a curriculum can be an excellent- tho expensive- way to do that.
As someone with a BS who in their 30s felt the same pull towards depth and went back to grad school- I definitely felt the psychic weight of being far and away the oldest student in my cohort. I got over it. It was great to be able to do the work.
In terms of opportunity cost- life is long. You have the rest of your 30s, your 40s, your 50s, your 60s- at least- to be doing productive interesting work, even if you don't need to be doing it for financial reasons.
Concur with others that the best option is to work for an employer who will fund some or all of an MS. Schools- even top 10 CS programs- in reality DNGAF whether you have a BS. For many, MS programs are critical money makers. They care that prospective students bring the $ and can demonstrate technical, organizational, and communication skills. There is an admissions process- their faculty operate a human-limited scale so your $ will be ranked against other candidate $. But some school will want your $. Start to make lists of schools/programs in areas of interest to you. You deserve to give yourself the chance!
Best wishes.