I was reading this question. There I read somewhere that he would have discovered modern physics if he had studied electromagnetism and nuclear physics.

It was most likely in jest. But I ask

  1. How much of physical,mathematical and/or technological advancements had been made in Newtown's time?
  2. Given the state of science politics & the real world, was it feasible to discover modern physics or general relativity for Newton?(given his genius)

It seems a really difficult work but the popular opinion seems to be that Newton was more of a genius than Einstein so I don't know.
After all, Almost every topic in classical physics has been contributed to by Newton. Every subject other than Electromagnetism has some important formula, law, approximation or theorem given by Newton.
If we consider him to be the inventor of calculus, then I guess he has a major indirect contribution to all of physics(classical or quantum)

While it seems opinion based, the question is really boils down to the scientific and technological condition of the 17th century. and a little bit on Newton's genius

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    $\begingroup$ In case you want it: In the parallel world where he did, he ended up discovering Special Relativity, which led to modern physics being developed centuries earlier. A nuclear war broke out in the year 1803, wiping out modern civilization. That's why in our branch Newton become disinterested in this topic. $\endgroup$
    – Alfredo
    Commented Dec 15, 2023 at 19:10
  • $\begingroup$ This was most likely the quote $\endgroup$
    – Alfredo
    Commented Dec 15, 2023 at 20:55