Indeed! Computer Recreations was the absolute best. I remember implementing an algorithm from this that displayed 3d projections of a 4d rotating hypercube; then extending it to support red/blue cellophane 3d glasses (or as best as possible with a 16 colour pallette). So much fun and learnt so much!
Yes, I have been using eshell exclusively for the last 7 years. It does have a few drawbacks, but for me it’s definitely a win overall due to a) everything being in a buffer, b) being able to run both elisp functions and executables from the command line, and c) tramp.
P.s. I chuckled a bit when you mentioned sixel graphics support as modern. :) Jokes aside, I have my own toy implementation of sixel graphics in elisp, so decent emacs support is probably out there already.