then my father (retired engineer) enlightened me on why important (electro-mechanical stuff) runs on older, slower, (but insanely reliable) engineering.

I am in the controls and automation sector. Your dad is half right.

1. You have to look at the whole system to determine reliability. Oh sure what you have now is going to last a long time but no one knows how to repair it when it dies. Plus all the components are no longer available so now a repair job is going to involve lots of work. I can't count the number of times I have had to bail out a plant because the one guy who knew how it worked retired. Very expensive.

2. Why do you need reliability? No really ask yourself this. Or better yet how much do you need. The answer is not going to be "as much as possible". Are you going to do this process this way for 30 years? No? Ok why did you pay 4x as much for a machine that can last 50? There is almost no chance whatever process you are doing is going to be the same forever. There will be improvements and your competition will take advantage of them.

3. What the heck does reliability even mean? Take a classic FET output vs a relay output.

Relays: easy to repair, can handle almost any voltage you throw at them, sensitive to vibrations causing false state changes, rated for a 10k cycles.

FETs: can't repair, can handle limited voltage ranges, ignore vibrations, rated for a million cycles.

Now tell me, given these facts, which one will result in less downtime over say ten years? I am asking here because I don't have enough information. Again you need to look at the whole system to determine which way you want to go. I have seen machines act up seemly randomly because a relay was flipping from vibrations and I have seen ones fuse contacts causing a machine to rip itself apart. I have also seen FETs die from a tiny surge.

4. Maybe you don't want a repairable system. I know this might be startlingly fact but it might benefit you to not have any ability to mess with your machine. Lots of amps and high voltage in these you going to have your guys open it up and mess around? Now you have the liability now your OEM can get pissed at you and not want to help because you messed with the design. You also compromised the UL label. The OEM can make a solid argument that if there is a workers comp suit that you altered it and hence it is on you. That's part of the reason why security screws are finding their way into factory equipment. Makes it that much harder to get inside.

5. I also question the mentality of customers who insist on individually long lasting parts when they haven't even established that they are. Sure NEMA contactors vs IEC ones look tougher but do you have data to back up that they are infact longer lasting? In real world conditions.

6. To put it bluntly: people get old and are afraid of change. They have half remembered wisdom about something that may have been true at one point but isn't anymore. The result is crap design. Fuses that don't protect anything, transformers that don't prevent surges, heafty parts that are a waste of material, line reactors when there is an internal one in the Soft starter/VFD, multiple voltage domains when 2 would have been sufficient, indicating lights that are dim, hardcoded non-safety interlocks when we have software, branch circuit protection when it isn't needed, expensive hard to replace push-to-test lights instead of a simple switch and software, thick wire crammed into limit switches that is almost impossible to repair, ancient PLCs no longer under support, serial comms that can't be troubleshooted, external power that defeats lock-out-tagout, roller switches that have to be made in a machine shop...

Oh sure your system will work but it radiants excessive heat, parts costs multiple times what they should to replace, large portions of the design do nothing but add heat and increase the chance of failure, it pulls a lot of energy, it can't be upgraded or even half the time incorporated into a line, it is more dangerous to work with, and you look like a fucking moron as people in the future learn not to buy a camel (horse built by committee) from you.

Don't go into controls/automation if you have any passion for good design. If you want to know what about a quarter of my customers are like imagine someone insisting that you apply the noose of a hangman to your forehead to fix a headache and women who show ankles carry smallpox.