But yes, it can be that deep - typography and font design is a very underappreciated field. Fonts don't just come from nowhere - someone has to sit down and design them, and it takes a lot of time and effort.

are people nowadays unable to be enthusiastic about anything without someone chiming in from the peanut gallery and calling it "cringe"?

Typefaces have always had a pretty passionate community, it can be surprisingly deep. A lot of people love and invest a lot of time in fonts and frankly paying some attention to design even if it isn't necessarily apparent is by no means a bad thing.

Behind every (well-designed) font is a world of typography. That's an entire industry at the intersection of science and art. Type designers take great pride in their work, and well-designed typefaces are practically timeless. Like good art, they transmit emotion. As a commercial product, they represent brands. A lot hinges on choosing the right type for a specific purpose, even if most of the general public is not consciously aware of it. So these announcements can indeed be deep and meaningful.

That said, the changes in this case seem very minor to me, as a casual type aficionado. I could barely tell the difference from Arial with both side by side, but I'm sure a lot of thought and effort went into this. Maybe it was worth avoiding the licensing costs? I wasn't aware Arial required licensing, though.

Another good reason to do this is to have a baseline font from which they can create different variants, or add new characters. This is probably why they were able to make so many proportions, weights, and slants. I don't remember Arial having a monospace variant, for example.

You actually have to license the typeface for many usecases. Even as a web service they were probably licensing webfont because Arial is not available on all systems so your Androids and Linuxes would see different font.

And yes the biggest reason to do this is to make your own tweaks without bumping into licensing issues.