I haven’t played The Sims since the first installment. But having heard the nightmare stories… sure, the game might be free… but everything, 99% of the game content, will be locked behind a paywall.
You want wallpaper? $2 for colors, $5 for designs, $10 for this holiday pack.
That doesn’t match with what I know; they make lots of individual expansion bundles, each with a fair amount of content.
The metric of “How to buy EVERY scrap of content for the game” is generally disingenuous, since most of its expansions are best enjoyed on their own, and you’d likely get tired of them after a few unless you really enjoy The Sims.