The WLTP states how many kilometers you should be able to drive if you keep repeating a very specific cylce of accelerations, stops, cruising distances at certain speeds, under specific conditions (temperature, road, usage of onboard electronics and heating/cooling, etc). It is in no way a realistic estimate, as you calculated. If your typical drive is a few km to get to the highway, and then a long drive at 100km/h, you wont get nearly as far - and it becomes exponentially worse at even higher speeds. I have found (having driven 160.000 km with a BEV) that the EPA standard used in america is more realistic, and can actually be achieved if you know you need the range. Drive it like the powerful fun car that it is, though, and your range will be about 20% below EPA, (30% in cold weather)
Also take into account that not all 90kWh are available to you; when you do calculations like that, assume 85kWh or even less.