This is not true, at least not in Europe. Wagons/sedans didn't disappear, we drive recent BMW 5 series and there are plenty of others (Audi A6, Skoda Superb, VW Passat, Mercedes and so on and on). Its as wide as it gets and you can buy official or unofficial conversion of back seat into 3-same-seat row. You just click a conversion layer into ISOFIX from what I recall.

It doesn't magically make back row wider, so you can't fit comfortably 3 taller adults regardless of seat arrangements, but 3 child seats are easy. It then has exactly same space as usual 3-seaters like Seat Alhambra, its VW equivalent etc. but you drive much better, more powerful and also safer car (ie frontal crumple zones).

If you think about 3 solid wide seats for 3 adults, such a car wouldn't fit in regular parking spot in most EU/Switzerland and struggled on narrower roads, yeah we normally don't do that kind of stuff here since roads and parking spaces are shared among everybody.