The 19th century isn't THAT long ago. Master Sun Lutang, founder of one of the martial art branches of Tai Chi died in the 1930s (1). There are folks alive today, such as Grandmaster Lin Chih Young (2) who can claim a lineage to him that goes back only three generations, and there are others walking around who are only four or five generations removed. These lineages are unbroken and, although some of the ancient material has, indeed, truly been lost, much of the Wu Dang / Taoism-based martial arts are still preserved and can still be "transmitted" to anyone willing to find these teachers and put the time in.

Many of these 19th century masters cross-trained in all of the related arts from that era and proceeded to carry down these traditions to their students.

Therefore, the original movements can, indeed, still be found in the world, and you can still learn them. You just won't see any of these movements displayed in Hollywood (because they're not flashy enough for the big screen), or in an MMA ring (because they're not designed for sport fighting), or through any school or lineage that remains or currently exists in China post-Cultural Revolution (because all of the true practictioners fled to Taiwan and elsewhere).

But you're right in that it doesn't AT ALL look like the Tai Chi that most of the world practices today. Many of the movements and forms have kept the same names... but they are trained and performed VERY differently from what most people would recognize.

(1) https://linnatural.com/about-our-martial-arts-school-in-coro... (2) https://en.wikipedia.org/wiki/Sun_Lutang

Full disclosure: I mentioned Grandmaster Lin specifically because I've met, witnessed, and learned from him directly having attended seminars that he's run in the past.