So let's discuss these questions:
To what degree is world-building needed to run a good/enjoyable campaign? How does world-building support depth and internal consistency? Can these qualities be achieved without a lot of world-building? What qualities does a campaign more likely have with or without a lot of world-building? What are the potential drawbacks to a lot of world-building and can it be excessive? Is it possible to "build as you go"? Etc.
It is certainly possible to build as you go. Whether or not I'd recommend that depends largely on how much internal consistency the players desire, and how good you are at remembering disparate facts and either linking them up or attaching new facts to them on the fly.
For many years, I played in a (non-D&D) game in which there was *exactly zero* world building done before characters started playing. The GM made us aware of this, that he'd be adding details as he went, mostly during actual play. It worked out fine.
But, to be honest, his ability to remember all the details, and make up plausible new ones as he went was above and beyond what I've seen in most GMs.
And, I note that he never tried to run a mystery plot.
