Whats wrong with microcontrollers for robust electronics?

[BrianHG]

Well, for super robust, you can design an all vacuum tube battery charger with old fashioned magnetic readout meters.
Properly done, it will survive a nuke EMP blast without fail.

I also hear that vacuum tube voltage references are super precise and immune from temperature and age drift.

[David Hess]

Microcontrollers have a higher threshold for reliability because they are so much more complex, especially when their programming is taken into account.

Reliable programming includes things like only using static declarations and fully documented state machines.

[Terry Bites]

Are these really your queries or just source of answers for other boards?

The customer is ill informed. MCs are good enough for aerospace.
They may be refering to Arduinos etc- which not really suitable for hirel, pro or industrial purposes.
A pro system will not have the unverified code, flaky memory and puny IO etc of a cheap dev board.

[coppercone2]

ehh keep in mind its government someone is gonna see 'light bulb changing technician' for your vacuum tube solution and it will get iced. And / or idiotic maintenance people are going to get inside the equipment.

the best solution is to keep people on treaties and foreign policy