Honestly, I don't get why people want a The Sims 4 Generations expansion pack when they can just buy that expansion pack for The Sims 3. There, problem solved.
Nowadays, Generations EP is also bundled up with World Adventures, which also comes with nectar-making and new harvestables. So... might as well just buy The SIms 3 World Adventures / Generations bundle for $20.
The Sims Franchise is a long-running franchise, and the weakness of being a long-running franchise is that fans would often compare the current version with previous versions to see which one would be worth the buy. Had The Sims 4 been the first Sims game ever, then it would be very attractive because of its novelty and uniqueness in the gaming world. But, because it's the 4th Sims game, long-time fans may expect more out of the game than in previous games, when Maxis had done a much better job with the base game and the expansion packs.