There's more than one good way to define "esoteric" but it gave me cognitive whiplash to hear the term used about lambda calculus.
I can understand that perspective, there are plenty of purpose-built esolangs which are very close to the OG lambda calculus, and depending on your background the whole thing might seem bizarre and unfamiliar and ancient and irrelevant.
At least logically I see that could happen, but my heart disagrees. I see lambda calculus as a root of the conjoined tree[0] which supports all of modern programming. It feels to me like calling written English esoteric because some people get by without reading and writing!
(I'm certainyl not saying you're wrong, but just that it's fascinating how different two valid perspectives can be.)
I'm talking about it not in the sense as the root of other programming languages but as a programming language in its own right.
If there is anything that helped me 'see the light' then it was this: that I could build anything with a core that small.
Coding used to be about learning about the mathematical underpinnings of computation and then learning a specific mapping from the math to the software implementation. These days we don't teach that to undergrads (or maybe they get it in passing in a survey class.) We don't teach parsing. It seems we teach a list of features you should expect in your Python implementation or Linux version. Maybe you get a class on SQL. It's astonishing to me that kids today can get a CS degree without learning what Lambda Calculus (or even Pi Calculus) is (are). I got a PHYSICS degree and took a course on the mathematical underpinnings of computation so I would understand why all that FORTRAN code I had to maintain looked as funky as it did. As best I can tell, our 4 year research institutions are a weird mix between day care facilities and trade schools. Just once I would love to meet a recent undergrad who had taken a compilers class or understood the difference between s-expr's and m-expr's.
File under "old man yells at cloud."
High-five! I also learned about all this as physics undergrad trying to escape from Fortran.
We should start a support group.