The city of canals,gondolas and tourists. Often too many tourists. It can also be expensive especially when it's brimming with tourists. So why go?
Venice is special in ways other cities only dream of. Fortunately most of that magic is accessible when the daytrippers are still dreaming in bed or have left the city for the night. The city at sunrise or after dark has a much different feel to it. It's more then the lack of people.
But there are ways to enjoy Venice even during the day. Offseason is also a pleasant time to go. Not only will you avoid the crowds but prices are lower. In addition to the summer high season Carnivale and Christmas both are high season. Carnivale being tied to Easter changes dates every year. The events last seventeen days.
If you feel like braving the crowds http://www.carnevale.venezia.it/en/
The Christmas period starts before Christmas itself and runs to the sixth of January .
Even during the offseason you'll have some crowds in the most touristy areas but it will be easier to find a quiet spot.
The weather during the offseason will be cooler. It's more likely to rain or at least be foggy. But it doesn't have to ruin your stay. The fog just adds a different layer of magic to the sights. So far no tourist has melted in the rain.
If it's extremely foggy you might want to pick a different date for a trip to the islands. The city itself won't suffer from the fog.
Venice itself is relatively small and most people can walk it from one end to the next. There are what seems like countless bridges making draging a suitcase difficult but once you've settled into your hotel the sites are well with in walking range. The local version of a city bus is the vaporetto. Expensive per trip. If you would rather not walk and intend to take the vaporetto consider buying one of the different passes offered. The multi day passes will save you money if instead of walking you intend to ride .
But don't think you have to. The main reason to take the vaporetto is the islands. A trip to the islands normally requires you buying some sort of vaporetto ticket.