I found I felt this way a couple of times when I built early layouts. I had this grand plan with everything automatic and 2 trains running and etc etc.
But once it was built, it got boring.
Many years ago I got interested in "operation" and came up with some ideas myself and then I got invited to friends HO layout that was big and was operated with a purspose. I found I was having much more fun and looking forward to each operating session (they are all different) and thinking of ways to incorporate more into my layout.
Look into one of the car card systems or switchlist systems for sending cars to industries and consider building a layout that has a bunch of places to ship and recieve cars. Actually you not need many.
When I first started I about 15 cars and 5-6 industries. One industry was an interchange with the C&O from my shortline. My operation was to take a loco from the engine house (it was a 2 stall not a roundhouse) and a caboose and run to the interchange on the other end of the layout. There I would pick up the cars on the interchange and assemble the train with the loco and caboose at proper ends. Each car on the interchange had a little tag on the roof routing it to an industry on the layout. I would then run around the layout and switch the 5 or so industries on the layout. Each car at an industry had the same tag, only it was turned over routing the car to the interchange, or in rare cases another industry. I ran point to point even though the layout could be continous. When I got to the last industry, I had a run around track in the "town". I would rearrange the train for the run back to the interchange. There I had to run around again and shove the cars onto the interchange track. This usually took me about an hour to do. It was fun.
I made different tags for box, gon, tank etc so they to appropriate places and I made more than I could use at one time. I kept them in a small box with separators on my workbench. After the train wsa done, I would flip the tags on the cars and pull all the ones on the interchange cars. I would then put new ones on the interchange cars. I tried to pick the new tags randomly. Voila, I had a new run ready to go. And if the tags had variation, it was guaranteed that the run would be different than the last since the cars and tags would be different creating different destinations.
Eventually I added a second small interchange track for the PRR too.
Every run would point out problems to fix on the la yout that gave me a worklist too.
Just a suggestion about adding something different to your running, but it might mean a new track plan.