It would be interesting to write a counter-factual history of the world if Marx had never existed
Worth attempting
A year before the birth of Queen Victoria
Bahadur Shah Zafar was just a 43 year old "young" prince
London with a little over 1 million people was the largest city in the world.
A v v long time ago
And yes, without Marx even, some form of socialist theory would no doubt have emerged in the course of the 19th century
It is worthwhile to attempt to identify the ideas that were unique to him, which you didn't find in other thinkers of the 19th century (Eg : Henry George)