Relative to the Lisp source, it might qualify, but wow. :)

Emacs 29.1, excluding the test directory; top ten languages:

    all          SLOC=2618374 (100.00%)     LLOC=182918  in 2584 files
    elisp        SLOC=1188181 (45.38%)      LLOC=0       in 1566 files
    man          SLOC=501820  (19.17%)      LLOC=0       in 48 files
    C            SLOC=387169  (14.79%)      LLOC=159681  in 317 files
    Texinfo      SLOC=288384  (11.01%)      LLOC=0       in 182 files
    Lisp         SLOC=175786  (6.71%)       LLOC=0       in 1 files
    Objective-C  SLOC=18289   (0.70%)       LLOC=8480    in 8 files
    Tex          SLOC=16031   (0.61%)       LLOC=0       in 23 files
    m4           SLOC=10436   (0.40%)       LLOC=0       in 133 files
    shell        SLOC=6819    (0.26%)       LLOC=0       in 28 files
    C++          SLOC=6240    (0.24%)       LLOC=2924    in 5 files

Ok, I should have said relatively, or even better "subjectively", small C source base.

The C base supports many platforms and variants, so only a part of it is used in a running Emacs instance. And to the 1+M lines of elisp one typically had many more extension packages. That's the the "relative".

In practice, when I want to change things I don't hit the C layer. Anytime I had to introspect Emacs to change something I was firmly in the lisp world. I don't remember having been limited by something being at the C level, which are things that cannot be changed dynamically. This is really what I meant: in practice to change Emacs the C level (although big in the absolute, and definitely complex) doesn't show up much and hasn't been a limitation at least to me.