The original transformer is an encoder decoder model, where the decoder model is what leads to first GPT model. Except you need to feed the encoder states to the decoder attention module in the original proposal, it is basically the same decoder only model. I would argue the decoder only model is even simpler in that regards.
When it comes to the core attention mechanism it is surprisingly stable comparing to other techniques in neural networks. There is the qkv projection, then dot product attention, then two layer of ffn. Arguably the most influential changes regarding attention itself is the multi query/grouped attention, but that is still imo, a reasonably small change.
If you look back into the convolutional NNs, their shapes and operators just changes every six months back in the day.
At the same time, the original transformer today is still a useful architecture, even in production, some bert models must be hanging around still.
Not that I am saying it didn’t change at all, but the core stays very much stable across countless revisions. If you read the original transformer paper, you already understood 80% of what LLama model does, the same thing can’t be said for other models is what I meant