Venice is always busy at San Marco. The question is whether you also get heat, floods, or Carnival costumes.
April–June and September–October
The default. Book rooms and St Mark’s slots. September still has warm light on the canal.
February Carnival
Masks, crowds, and a city as theatre. Book far ahead. Not a quiet lagoon trip.
November–January and July–August
Acqua alta risk in late autumn. August is hot and cruise-heavy. Winter is cheaper and atmospheric if you pack for wet stone.