I'm not sure why VCE would be a particularly apt comparison apart from the similar airport codes, but more importantly, your summary above is actually incorrect. There are busses at VCE too, and in fact a higher proportion of BA flights get them, especially in the summer when several of the BA flights from LCY/LHR/LGW have overlapping times (LCY/LGW in the morning, LGW/LHR in the evening). NCE has a lot more BA rotations and typically the same absolute number of them using bus gates (either 1 or 2 a day in peak summer mostly).

I actually absolutely love VCE airport, so certainly don't expect me to criticise it. Like you, I really love the lounge with its open terrace (but that's very unusual in Europe, though there are a few similar examples in Greece/Cyprus), which is a wonderful place to sip a spritz, and obviously heading to the city with vaporetti is magical. I also enjoy the "DIY connections" which are fun.

That said, getting to the city be it by public or private transport takes at least three times longer. It is also massively more expensive. Public transport to Venice costs €15 whilst in Nice, both bus and tramway will cost you €1 per trip if you buy a carnet of 10 (available at the bus kiosk just outside of arrivals) or €1.50 if you just buy a single on the spot. Typical uber to Nice city centre will cost you between €10 and 18 and take 10-15 minutes, whilst any private transport in Venice will leave a serious dent to your bank account.

Nice also has two different types of fast track (again, it's only that BA choose not to pay for it but that's not the airport fault), and unlike VCE, you get lounges in every area, which means that you don't have to double guess how long immigration will take and cut your stay short as is the case in Venice where the lounges are only in the Schengen area.