for me it changes from time to time. at first my favorite thing was gardening (I guess using features from seasons) and I used to play legacy style. and I liked making my legacy family do impressive things, like maxing careers and reach particular milestones. but that bored me quite quickly...
then, I got more into gameplay centered around a storyline that I made up as I went, more or less. I believe I managed time poorly, my sims barely aged and I kept getting bored of the same group of sims. I still play that save but I do get bored of it sometimes.
however, my new favorite thing to do is playing entire nbhs. by that I mean playing all the 4-5 households in one particular nbh (while the rest of the save is managed by mccc - rather chaotically but I don't mind that). I play 1 week per family and with aging on for everybody (long life span) - this for me has been a game changer, since managing aging has been a problem for me before. I feared my sims aging and dying, but in turn it caused me to get bored of them at some point.
Having all those households interact with each other, forming a variety of groups (get together), focusing more on experiences with those families (with the holidays in seasons and vacations to different destinations and going to restaurants) and less on reaching some arbitrary milestones in terms of their performance or money, having sims have casual hobbies (from any pack, really). Something I also enjoyed was taking things slow and not rushing relationships of any kind, promotions or skill improvement... I also play with the mod wonderful whims, which has an attraction system, which can create some potential mess, because sometimes sims are more attracted to some nbr than to their spouse, so that's a fun thing to keep in mind.
I plan on playing this way throughout another generation or two, keeping my favourite sims from those families and moving them to a different nbh once I get bored of this particular one, fill the rest of the homes with some new sims and starting this process again in that new nbh. I have to say I still have a lot of exploring to do, as I haven't tried out some features of some packs, like the actor career, or off the grid life in sulani. I'm also excited to recreate this gameplay style in some nbh of san myshuno and mt. komorebi.
something I guess is important too is having very different households, I wouldn't enjoy this play style with 4-5 functional, conventional families, I enjoy some variety. as an illustration, right now I'm playing a single dad with his toddler, the bff household, a single lady in a haunted house and a lesbian couple who adopted a toddler who all live in Foundry Cove, Willow Creek. the 5th lot there is a community park filled with activities for toddlers and children, stands with food and the voting thing from Eco Lifestyle.
one last thing. I used to not like toddlers and kids, but I found it's more enjoyable for me to not really control them directly, rather have the parents or siblings take care of all their needs (which is how it happens irl). the parenthood pack is amazing for this, imo. you can encourage kids to do things, punish or encourage different behaviours with a variety of reactions depending on the kid.
