The reason the other games lasted 4 years was because they could only last 4 years. Sims 1 really was showing its age at 4 years, and Sims 2 and 3 had the same engine, so they were bound to last roughly the same length of time.
Sims 4 doesn't feel complete, nor does it feel like there's something that could replace it.
People play Sims 4 on laptops that struggled with Sims 3 and expect to be able to play Sims 5 easily, and say "I'd be happy to buy a new computer for SIms 5 if it's good,". Like a gameplay PC is the free prize inside a box of cereal. Oh, and like Sims 5 base game will somehow be more complete than Sims 4 base game.
