So... I kind of agree with those against this concept, but not exactly for the same reasons. Now, I certainly don't know everything about game design, but I do try to pay attention to the process and I have had opportunities to have conversations with people in the field. (Not the Sims team.) So these are my thoughts on it...
First, Sims 4's engine, which was initially intended as an online game, was a HUGE disappointment to those of us who played any of the previous Sims games. The comparison was so drastically inferior to the game quality and features we'd had before because when you build a game intended for massive multiplayer, it means you lose some of the flexible features of a single player game. For example, in Sims 2 and 3, we could edit the neighborhoods around the lots and even create our own worlds. But in Sims 4, the worlds are all static and unchangeable, which was a huge step back from the classic innovation of the previous games. This is why we're always stuck with what everyone calls "set dressing" and limited lot space. In Sims 2 and 3 we could actually place our own lots, choose our own lot sizes too, and we weren't limited to what the devs gave us so we could have more rural, sparse neighborhoods if we wanted or we could have something that looked more urban/suburban. I miss those features so much, I really want them back for the next game so I don't have to have the same darn playgrounds and picnic tables and grills in every single neighborhood. I like a very different aesthetic and I miss being given the creative tools to create it.
My second issue is probably the unpopular one, and that's the open neighborhood. I think this request comes mostly from Sims 3 players who got used to the open world play, but, again, when you get a new big feature like that, it means taking something else away to avoid overload, and unfortunately, Sims 3 took away proper rotational gameplay. As rotational gameplay is my play style (I have many Sim households that I like to switch between) if they were to go back to the "open" concept, there's a large chance my play style will be cut, and then I won't want to play the game at all because I'm way too easily bored with single households, even if there's a lot of Sims. Another thing about the open neighborhood concept that would concern me is, even if they find a way to keep rotational play, it would still mean potentially having a lot of active Sims at once, which could cause them to reduce total household size even further. (In previous games, pets didn't take up a household slot, so that's something that already got gimped in TS4.)
My Third point is really the same as another person said in this thread. Multiplayer design means multiplayer resources are needed, which means a little less resources for single player features. This can include world designs, creations, assets, patches and maintenance, even bug fixes take resources. The more they give to multiplayer, the more they take away from single player because resources are not infinite, they must be allocated. I'd be fine with a separate multiplayer game using Sims 4 engine, but I'd like the next iteration to steer clear of it.
I will say though, the idea of being able to import current Sims and owned content is intriguing. So I do kind of dig that idea. And as for the new look, I just hope it's not too realistic. Realistic art styles tend to age badly, in my opinion.
