I have thought the same thing.
Of course there are a few fundamental differences between then and now from my point of view:
1. I was a young teen and had tons of time (and energy) on my hands to play with these things.
2. Everything you learned you figured out on your own or as a group share with close friends, supplemented with a few manuals and magazines.
3. The hardware was finite enough you could basically learn everything from the low level access to the hardware to all the software features (basic or machine language). You could literally learn what every location in IO or memory did (53281 anyone??).
4. With a few days or at most weeks time with even modest skill levels you could put together something that could "wow" your friends and perhaps even non-computer family members.
5. Atari / TI / Commodore computer overnight parties where a bunch of us get together to compete to show off the best games etc. in an attempt to prove we had the best platform.
Today we have a lot more learning resources out there, and the hardware is much more powerful but in my mind it just isn't as fun. There is certainly no way to whip up something that would "wow" anyone. It's more a tool now than a fun hobby.