When I take a look at my list of Meme Machines we can classify these into three strands...
1. GOFAI - Good Old Fashioned AI
These are based on some kind of predicate logic and use languages like Prolog or LISP. START by MIT is one example.
2. Pattern Matching
One of its prominent examples are engines based on AIML, Artificial Intelligence Markup Language, like A.L.I.C.E. Up to now these AIML based chatbots achieved the best results in the Loebner Price competition.
3. Neural Networks
I guess it really took off with Google's BERT, the introduction of Transformers, in 2018, and now the race is up to create models with more layers and parameters to achieve better results in text comprehension, question answering (SQuAD) and summarization.