I wonder if it has become easier to use and more useful.
I had a brief stint where I became exited about it (based on what I later came to view as hype), and spent some effort trying to make it do cool stuff.
I ended up abandoning it for a number of reasons.
I've served time with a number of 3d tech through the ages.
My favorite was VRML from 25 years ago (sigh..),
which to me is still unmatched
- you could open up a notepad file and just plunk in
a 3d model structure in ASCII, then load it immediately in the browser
AND WALK AROUND IN IT.
Sadly, the browser plugins were binary, and have died
out together with web browsers you can no longer download or install
(Netscape, where are you?..)
If you like pain, you can still get hold of "client technology"
that will run (some) VRML models, but you must like pain,
both to get hold of them, and as you afterwards try to run and use them.
So yeah, VRML is gone, I know.

Then there is AFrame.IO, which I've used some.
It doesn't offer much, so it doesn't disappoint on what it delivers..
It is probably the closest to VRML, but sadly doesn't offer as
good an experience as we had around 1999/2000 :-/.

So, I've tried babylon.js. My gripes with it are:
- for the usual demos it loads, it doesn't seem to have a
'preferred navigation feel'.
- it doesn't seem to care for planet earth physics much.
I'm probably not describing this aspect the right way.
VRML used to have 1.0 units correspond to 1 meter,
and people would size their content based on this.
Similarly, rendering client navigation would base on this,
so you would move around at speeds akin to walking
- it would even default the viewpoint height to 1.8 or something like that
(to resemble a human being about 180cm of height.)
It's about the look&feel, how it FEELS when you try to navigate the 3d world.
If it feels janky, not smooth, that is bad..
And if 10 different 3d/VR experiences have different navigation model feels,
that does not feel good to the end user.
VRML had this down - in 2001.
TL;DR: Default navigation UIs in babylon seems like
a kludgy afterthought, instead of a "Steve Jobs design priority".

Another example: Setting up a default test scene.
If I were trying to push my 3d engine/tech to people,
I would prioritize tools to set up small "hello world" scenarios.
Supporting a good 'hello world' is not frivolous.
It is about selling your tech, and convincing.
If I try out a small demo, and I feel it is intuitive and easy,
and that "I am in control", I think 'Yeah I can build something on this!',
and get the impulse/momentum to want to build something in this.

Again, VRML did this well:
You could set up a scene in like 5 lines of code.
For example, you could specify a sky sphere, or a sky box,
with 3-5 lines of code.
I would often do a 3d world, where I started specifying a ground
and a sky and colors for them, with such 5 lines.
Being able to load your 3d scene already with this and
walk around in it, is COOL! It makes you want to "put further stuff in there",
because you can already see it.
Babylon.js, in theory, has similar stuff.
But if you try to actually use it, you find out
that it wasn't really intended for general use,
and not really intended for any real use either,
it seems more like a sort of 'can't you throw _something_ like that in there?'.

_SOMETHING_.. - not something good.
So - another strike - for setting up a basic sky and ground, babylon.js
is worse/not as good as HTML from 25 years ago :-/.

They may have fixed some of this, but past disappointed experience
makes me reluctant to take the effort to check it out again :-/

Another thing that put me off: I never found any community
actively using babylon.js, at least not that I could find with google?
(Discord & your ilk be damned.)
I found reddit's /r/babylonjs, but it was mostly empty,
apart from release announcements by MS, and random demos done by MS people.
So if there is any active community using BJS, I haven't found them?

What I've mostly used instead, is
- the roblox engine (I use all this to try out ideas, not to serve a commercial purpose.)
- the GODOT engine, which I am willing to praise as high as I am willing to .. not? praise babylonjs?
- Unity, but for what I do, roblox serves as well, plus I don't have to handle publishing.

I had high hopes for babylon.js - as a wrapper that would shield me against three.js changes
- but I am still looking.