I think auto-exposure doesn't necessarily mean less reliability. Plenty of trapped-needle fixed-lens RFs made in the 60's still work well. But with the focal-plane shutter models, AE does imply electronic control, battery-dependence, and that if the electronics goes south, the camera is dead. Electronics usually either works or it doesn't, while gears and pulleys and such mechanisms gradually deteriorate and make funny noises.
That's not to say mechanical complexity might be any more durable, but can usually be fixed even if it means fabricating an unavailable replacement part. I am fond of my M2, and at least equally fond of my Minolta CLE, which I admit is at the camera doctor with sick electronics.
One of the first SLRs with electronic shutter control and AE was the Pentax ES (Electro Spotmatic). I got mine in Dec 1972 and it still works fine. Now there's a solidly-built camera!
I value the AE feature, helping me cope with rapidly changing light conditions, as with following action that moves through different illumination. The event that illustrates it for me happened in 1967 at a political demonstration on a street corner where two speakers started slugging it out, and in doing so moved from the sidewalk into a much darker market area, and then back out again. I quickly cranked open several (insufficient) stops but AE would have been nice right then! I got the Pentax ES when introduced a few years later.
Using a camera on manual with occasional incident meter readings is a fast way to shoot, and a sequence of shots in the same light will then have more consistent density and be easier to print with the same enlarger settings, but there are times when AE gets the picture better. And I prefer a simple center-weighted meter pattern, easier to know what it's up to!
I have been very negative about Auto Focus in the past. As a test, a couple years ago I got a Fuji GA645W that's essentially a big P&S, and more recently a Contax G1. I'm still somewhat negative about AF, certainly not a devotee, but once I learned how to make it do what I want, it can be handy within its abilities. AE and AF can allow me to pay less attention to mechanical details and more attention to the subject & composition.
I'll have to think whether there are certain subjects where all-mechanical minimal-automation is better. I say "minimal automation" because even my Leica M2 has an automatic frame counter, manually reset to be sure, and an automatic link between the rangefinder focus and the lens focus. "Newfangled" SLR models like the late-50's Pentax introduced an automatically returning reflex mirror, then then almost before that shock was absorbed they came out with a lens diaphragm that not only closed down automatically but opened back up instantly too! "What's photography coming to?" must have wondered Pentacon and Exacta owners.... 😀
Anyway, I suppose more static photographic pursuits like macro, geometric studies, landscapes, still life and other studio work would find little use for AE & AF, but maybe they could use a motor film advance... Oops, too fancy? But isn't the Pentax 645 with AE and AF and zoom lens rather popular for landscape use? Hey, whatever floats yer boat! 🙂