1, 2, and 3 did not need to make previously paid for DLC free to be good and solid games. You still have to pay a premium for 3's content to this day. It is not that DLC systems cannot work, much less the usual pack systems the Sims has always had, just that the base game is not sturdy enough and the updates are lacking.
Point to No Man's Sky all you want. I have the game myself. It is the top redemption story of industry at this point, the way it gets thrown around. It is not really a paid DLC game, though. It does major free updates, which the Sims... Is only sometimes on board with? We have got some good ones, but they do not update DLC content (which is kind of odd) and they seem fairly rare in comparison.
If I had to pick a method, I would say the Paradox method (which is what I think 4 somewhat attempts to do), which is for every pack there is a substantial base game update to connect and enrich the two. And, if necessary, DLC stuff gets adjusted.
Beyond issues of unwanted content/changes (and if you are skeptical of this, look at anyone asking for supernatural nerfs or some of discontent surrounding the new eating time change), even if you packaged the first 3 years of DLC into 4 it would still be lacking. Perhaps they could, emphasis on could, do more with the features in the future (or would have done so anyway when they single out a feature for usage), but aliens suddenly being base game would not make 4 or 4's aliens more fun. They would need updates expanding their features. You cannot ignore step two. Just adding old packs alone will not do it. They have also, for example, updated vacation systems without making Outdoor Retreat base game and it was the first pack. They can do related base game updates without adding DLC content.
All in all, why add every part of an old DLC people paid for when they are not even going to update the features to make them better for everyone? So they hypothetically could in the future? The pick and choose method didn't stop them with photography, etc. So, no, I think we need more updates to all content. Just adding in old packs and calling it a day would only upset people.
