The reason the Star Wars and Inside Out playsets look more 'complete' is due to them having a common theme to them.
With the Toy Box Expansions, it mashes up different IP into a mode linked to each expansion. I saw an entire playthrough of the Takeover expansion and visually it looked very nice and it felt like a full game. Just one using different Disney/Disney-owned IP throughout instead of just focusing on one of them.
The Toy Box Speedway will function similarly to that, with a small racing hub and a portal linking you to different race tracks/modes using different IP.
Both are complete experiences and have solid production values, its just they aren't as 'detailed' as the other playsets due to them not focusing on one core thing like the other playsets.
Long story short; don't write them off due to them being cheaper and/or 'looking' cheaper then the other playsets

.
Edit: And also consider that Sumo Digital is developing the Raceway playset (like how Ninja Theory developed the Twilight of the Republic Playset) and a look at past games they developed shows how they can make amazing looking games. Sonic Racing Transformed is a great example of there work on a number of levels, as is the Outrun games they developed in the past

.