Everything after JPEG is still fundamentally the same, but individual parts of the algorithm are supercharged. JPEG has 8x8 blocks, modern codecs have variable

Everything after JPEG is still fundamentally the same, but individual parts of the algorithm are supercharged. JPEG has 8x8 blocks, modern codecs have variable-sized blocks from 4x4 to 128x128. JPEG has RLE+Huffman, modern codecs have context-adaptive variations of arithmetic coding. JPEG has a single quality scale for the whole image, modern codecs allow quality to be tweaked in different areas of the image. JPEG applies block coefficients on top of a single flat color per block (DC coefficient), modern codecs use a "prediction" made by smearing previous couple of block for the starting point. They're JPEGs with more of everything.