After the disastrous experience the publisher had with the launch of the online-always SimCity, which resulted in gamers boycotting the purchase of the game due to connection issues, EA wisely opted to have The Sims 4 single player be an offline experience.
EA's also promised with The Sims 4 that there would be a new "SmartSim" feature, which is meant to streamline house building, compared to previous iterations of the game.
Well I have TS2 and personally designing the house is one of the funnest part, but if its an option then it shouldn't be bad.
I have heard that TS3 had some regressions from TS2 but I have never played it to say for sure. I do hope that it it holds on to the better parts of the game though.