I've felt similarly about projects. I can't get motivated simply by making some pointless circuit, I always need a concrete goal.
As mentioned above, something that will keep you occupied for years - home automation.
There's a ton of plug and play stuff out there, but there's also tons of standardised protocols and interconnects that allow you to make your own devices that tie into a larger system.
At a quick glance, you'll need to utlise:
- Analog electronics
- Digital electronics, I2C, SPI, RS485 etc
- Programming microcontrollers to run your modules, tieing together the digital electronics with software protocols like MODBUS, MQTT etc
- Setting up a mini computer / SBC and running the software, ie, containerised stacks, python coding etc
Every step is like a side quest.
One more thing: these days I would not recommend the older Atmel 328 or 168 based microcontrollers, unless you're doing a really simple sketch. I've found weird bugs with them once you start to get into more involved sketches.
The more modern versions like the 4809 based Nano Every is certainly more expensive, but more capable and I haven't found any bugs so far.