That tldr needs a tldr…
But also you absolutely can learn & build small versions of LLMs on a regular laptop. I did it on my old 2017 Dell XPS, and trained it on the complete works of Shakespeare. It learnt to write almost passable Shakespeare hallucination in a couple of hours. There’s a good tutorial online if you search for it.

Oh sure. The training data is about 5mb so easily manageable on a relatively modern machine, but not on the kind of thing that was used for ELIZA.