Literally every AC games takes elements from the one before it. I'm sure I'll miss a million others, but these are some of the things that come to mind:
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City Folk had the shopping area, Shampoodles and the ability to add a few buildings. These features were present and improved in New Leaf.
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New Leaf - Added new character customization (hairstyles and skin color through tanning), house customization (like themed exteriors and fences) and gave players an occupation in town. With Amiibo cards, and Wisp's lamp, we could call villagers. All of which made it into the next installment, Happy Home Designer.
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Happy Home Designer improved home decorating (even including things like blinds and other window treatments) and added more items to the catalogue. Skin color became permanent, which meant players no longer needed to tan their characters. These were all included in Pocket Camp.
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Pocket Camp has added new hairstyles and the system of collecting materials to craft. These, plus more, will be in New Horizons.
Of course there's gonna be similarities, that how AC has always worked. That's not a bad thing since there are constant improvements on the things they pass on to new installments. I don't mind DLC, since it's optional, but I'd rather wait to see what all Nintendo has in store before being upset/disappointed with unconfirmed features.
Edit:
I wish they'd think about adding farming XD