My feelings

The way I see it, TS4 is a 10 year old game, people can take a break from playing, especially if they have played since TS4 was released. Then there are the players who have been with the franchise since the beginning, maybe they were teens or early twenties when they started playing, and in 25 years their priorities have changed and don't play as much or as often they did. When they say losing players I would assume the players have left the francise for good, don't play and therefore have no incentive to buy new packs. Personally, I don't know anyone who woke up one day and said that's it, I'm quitting the Sims for ever. It is summer, many are probably on vacations enjoying the sun and touching real grass. They will be back playing the game when they are ready and feel creative again and the game is a great creative outlet even if there are some bugs. Don't worry about what other people are saying or how they play their game, this is a single player game not a MMO. If the game feels right for you and you get some satisfaction and joy out of playing it, then it is worth it for you.  Don't buy packs just to buy everything, buy them if you feel like you want to explore the additional content they offer, because it may happen that people praise certain features, but when you try them out in game for yourself you find out that you don't like them as much as those other people do. But just as well it might happen that you get an idea about a storyline and a pack other people didn't like feels just right for you and your game.