"Before this, I had thought that C was a simple language."

It was a simple language. It can still be used that way

As hobbyist I write simple programs that can be compiled with -std=c89

I use these programs every day. They are faster than their equivalents in python, smaller than their equivalents in go, and require less resources or dependencies to compile than their equivalents in rust

It is easy to take something simple and make it complex

Software developers do this consistently; software/language "by committee" faciltates it

Generally developers commenting publicly do not like "simple", they prefer "easy"

C89 is still useful and there are lots of things that rely on it

C the language is simple until you actually have to do something useful with it then you have to memorize the apis of every library you import.

I have done something useful (to me) with "C the language"

Generally, I do not use any third party libraries besides the "standard" ones that come with UNIX-llike OS

I do not _have_ to use other third party libraries, it's a choice; I choose not to use them for personal reasons that may or may not apply to anyone else