I think most of my embedded projects aren't that useful, but they've taught me a lot.
In my book, impractical means "I built a cuckoo wristwatch". Beyond impractical: "I built a cuckoo wristwatch but there was no room for a working mechanism".
I enter most of my learning project from the assumption that I could just buy/install whatever I am building and save time/money.
Please consider seeing things from a different perspective than "your book".
Not saying this to antagonise you, but because a lot of time reading comments like this makes other posters less willing to share their impractical efforts, and would love to read more of those, not less.