How do I make Sims 4 more fun?

I was having the same issue.
I find I get bored if I have big families or adult sims who work off the lot. I try to make smaller families, starting with one or two sims and maybe having one or two kids. I try to do work from home jobs and I've really been focusing on my Sims aspiration goals lately. This is something I never focused on, but they are fun and get harder with each level. You can always change it if you aren't enjoying the current one.
Try hobbies and jobs your sims don't normally do. I'm working on the conservationist career and i'm loving it!
You can always set your own goals for your Sims as well. I use to write down 4 things I wanted each of my Sims to accomplish. I find starting a new family can be boring because they lack interest and have no set skills. But once you get skill levels up, it's more amusing. (You can always cheat on this.)
There's tons of challenges online that you can try as well. I could never get into them. I'd rather just do my own thing.

"jimbbq;c-17451050" wrote:
Install mc command make up stories. Use kill sim to create a serial killer.

Create a family then use mc command to make them enemies to each other and see how it pans out.

Use mc command to add a very sad mood (depressed) that lasts for 20 days. See how your gameplay might change.

Use mc command to reduce motive decay if you struggle with filling needs.

Use ms command to create complicated love triangle and play rotationally.

Mc command rules.

Lol wait what?! That’s insane! I’m gonna have to check it out

I send my sims to Selvadoria to get into the local culture, make friends, build the skill and such. Along with that it's into the jungles to explore, find things, build that skill, and find the plants & fish that are only there. Great way to have lots to do, even when home, and broaden simiam horizons. In one case I may have a wedding coming up soon as well.