I disagree with the idea that holding onto Sims 4 is due to "sunk cost fallacy", at this point it is more of a sunk cost reality as general cost of living rises. What this means for a lot of long time players like who grew up with Sims from teen to bill paying adult and never got into streaming is that if support of Sims 4 ends players like me won't move onto a whole new separate Sims 5 just to spend the same amount of money to get all the same DLC equivalent all over again. I have other commitments and hobbies so I will just not be a EA customer anymore. Given the potential size of this demographic I suspect EA and Sims devs decided trying to go for a more gentle slow replacement with updates and bug fixes so as not to burn down years (maybe even decades) of existing player base goodwill is the smarter marketing. And because base game is free to play financially it makes sense when their sustained revenue is from long term players who are most likely to buy more DLC steadily over time to keep it fresher. I'm not saying you haven't got a point with the bugs and the lag, but they're a business so I'm fairly confident they've mulled over the alternatives and possibilities many times over long before they decided to announce their decision. And I'm pretty certain my guess as to the reason why is no small part of it.
