Maybe don't build a city on 118 small islands and expect the water levels to never ever change? Seems more like a failure to plan for the future.
It's honestly not unreasonable to say "Oh hey the place you built a city is no longer cost sustainable" but there are multitudes of villages and towns in europe, the fact that we know about Venice today and don't know about Ormelle (a random village north of Venice) means there were some reasons for that particular location to prosper.
Lastly, we've got the hand we've been dealt and I think it's quite reasonable to try and preserve this historical city even knowing that is it in a vulnerable location, that isn't really a global decision but it is going to be influenced by how many people still find it worth the money to visit.
But now that the structures are considered historical and preserved, they're trying to maintain a particular snapshot of the city, with the exact same buildings. Which is a lot harder than maintaining the city overall.
If humans weren't polluting the atmosphere, the climate would still be changing. The only difference is time scale and possibly the temperature delta.
This is why building cities right up against the shoreline isn't a very good idea in the long term. And, no, you can have ports without building metropolises right next to the water. Someone's going to say that I'm a "climate denier" which is totally false because I believe in anthropogenic global warming.
With climate change, we're looking at drastic coastline changes over the next 100 years. 100 years is extremely short for cities - it probably takes about that to go from being a town to being a city, if you have excellent growth rates.
To move a city in 100 years is probably flat-out impossible, just for cost reasons alone. Most cities are hard-pressed to pay for maintenance of roads and essential services, and service their already crushing debt levels. City governments are not going to manage it, which means the citizens of the cities are going to shoulder the costs. We're going to see large-scale financial hardship in coastal cities going forward, and multiple cities going bankrupt and into decline.
[1] https://ocean.si.edu/through-time/ancient-seas/sea-level-ris...
Scale matters a lot.
Venice will likely have to take similarly-drastic measures, and they're a lot harder to take given that modern-day Venice is much bigger than 1850's-1860's Sacramento.
Frankly the problem with Venice is not where it's built or climate change. The problem is that Italy has become a country living by the day and entirely unable to discuss and plan and act seriously for the future (or the present, for that matter).
The MOSE project that should have saved Venice from the high tides has been discussed for almost thirty years before even starting the construction, which then proceeded at snail pace with stops and go, lack of funding, corruption, and political quarrels.
Nature has never been benign. There are countries that are organized and efficient and dominate it- see the Netherlands. There are others that spend time in squabbles and suffer from each flood, storm or earthquake- see Italy.