The writers really broke the mould with the Monica - Chandler relationship.
Ross and Rachel is the usual blue-print for couples getting together in a TV show - a protracted, will-they-won’t-they scenario, one liking the other and the object oblivious. Then the other realising their feelings, then on and off again. They even used this blueprint with Joey and Rachel.
With Monica and Chandler on the other hand, they got together without ANY sort of build-up for the audience. And then once together, they were solid as a rock. The theme was - it feels so right, why haven’t we always been together?
Chandler and Monica liked each other, as much as they loved and fancied each other. They were friends who wanted the best for each other, they made each other laugh, they took the piss out of each other. It was a really healthy relationship, in contrast with Ross and Rachel’s frankly quite toxic relationship.
They both ‘came of age’ in their relationship - it was easy, highly functional and mutually satisfying. They grew up and eschewed all the nonsense that held them back in previous relationships.
I thought they were perfect for each other.
And as my username suggests, I’m a Friends fanatic. 😉