Lighter??? You mean thin? Lowercase is what, short like the 'x'?
That is exactly the opposite of a good programming font. These characters should be extra-tall. They should go at least as low as any other ASCII character, and at least as high as any other ASCII character. An extra pixel (or several on a 4K display) upward would be even better, up there with the accented uppercase letters like A-with-ring.
I'm using the standard terminology in the font industry. My borrow font for brackets is called SourceCodePro-ExtraLight, not SourceCodePro-ExtraThin. And yes, lowercase as in the same height as lowercase letters. That was an interesting experiment that I rejected. I prefer light (thin) brackets that enclose everything, as you say.
Lisp is in decline in part because of the community tendency to circle the wagons in the face of any criticism. My single point is that Lisp parentheses are always too heavy, and readability improves with lighter parentheses.
I've also long used Unicode replacements for => and other combined symbols in Haskell. Then I discovered Hasklig, solving this problem instead through ligatures. Any problem one can solve in the font itself is transparent to the rest of one's tool chain. I'm a convert.
That is exactly the opposite of a good programming font. These characters should be extra-tall. They should go at least as low as any other ASCII character, and at least as high as any other ASCII character. An extra pixel (or several on a 4K display) upward would be even better, up there with the accented uppercase letters like A-with-ring.