I actually think the OP and the comments are too focused on the programmer-related aspects of this. I'll add a few things. 1. It's not trivial but it's not that hard if you have a decent vocabulary and some intuitive sense for word frequencies (and word pair frequencies) for different locations in a word. The answer list does not seem to include really hard words as naively picking all the words in the MW dictionary…
#1 is why it's so successful. It's just challenging enough to make you think, but still solvable by most people. So we all get that nice dopamine rush of solving a puzzle with a reasonable perceived effort. How many people don't play the NYT Sunday Crossword b/c they never get more than a few words? There is a very devoted fan base for crossword, but it's not as universal as Wordl's adoption. To me, that's the genius…
The NYT Crossword Minis is actually really popular within my friend group. It's usually about 8-10 words.