Is calculation the most important aspect of playing chess? In many of my games, I've come across opponents who can calculate really well and deeply. Generally I feel that I lose if I can't calculate as well as my opponents. So my question was really if calculation was the most important aspect of playing chess. Would the person who calculates better normally win?
Would the person who calculates better normally win?

If everything else is equal then the answer is obviously &quot;Yes&quot;.
However, everything else is rarely equal. Fixating on calculation is very common in chess players. Here is another question about calculation which clearly demonstrates this fixation.  The fixation is so clear that the best answer easily pinpoints this in the first two paragraphs. BlindKungFooMaster then goes on to make the key point which is -

In my experience ratings first and foremost reflect positional
understanding. Calculation skills make a much smaller difference, at
least above a certain threshold.

This fixation with calculation is, when considered rationally, obviously wrong. The strongest chess is not pure computer chess, chess based on pure calculation, it is correspondence chess where a human being moderates pure calculation with their positional understanding.
This was certainly the case before AlphaZero. AlphaZero's recent success is down to an attempt to incorporate positional understanding into computer chess which has worked better than more simplistic ideas like adjusting scores according to ideas like doubled pawns, central knights versus dim knights on the rim, king safety in the middlegame, centralised king in the endgame, etc. It would be very interesting to see correspondence players being able to use AlphaZero-like computers in their competitions.