"you need a lot of simple things packed into this complex thing which is modern computers"
The above misses my points but allows me to make them again: simple is good, and, when laid out and raw anything can be understood.
If the 'resource management' you promote can only be understood by the few, the 'expert', then that 'system' must be viewed with suspicion.
And: I answered your question...here, let me do it again:
Q: Would a simple computer be able to do much?
A: It would do what it was designed to do. That is: as long as you asked the 'simple' computer to do what it was designed to do, it would do it. The more you ask of it, the less capable it would be. Networking simple machines together nets you increased capability...building more powerful (complex) machines nets you increased capability...in either case: simple leads to complex...if you can understand the parts, you can understand the whole...your 'resource management' scheme must bear up under similar scrutiny or -- again -- it should be viewed as suspicious.
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"virtually worthless in modern construction work, and quite tedious to use"
HA!
Go talk to a construction worker...ask him what uses he has for a hammer...tell him the hammer is 'worthless' and 'tedious to use'...prepare for ridicule.
Anyhow...

...all those machines you cite (nail gun, cement trucks, etc.) wholly understandable by the average shmoe if said schmoe is inclined to take the time and effort. No 'expert' is needed to, replace a valve, hammer out the bend in a nail magazine, change a belt, change the oil, replace the brakes, bang out a dent, etc.
Similarly: no 'expert' is needed to understand what motivates a man or woman, what drives an economy, why societies function as they do, etc.
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"Google: insanely complex"
No, not really...don't take my word for it...research it yourself.