bertbusdriver
Smash Ace
There's an edge guard case where they recover above ledge (high illusion, firefox to ledge) where you don't have enough time for anything but ftilt since it comes out on frame 9 whereas fastest upair and nair are like frame 11 and frame 12 or so (also frst frame of upair doesn't covers a very small amount of vertical space since falcon's legs are like horizontal or 4 oclock position). You usually have better options, but there are times when it is a legitimate option.Neither are good edge guard options as neither scrape below the ledge.
That said, I agree with your general sentiment that the tilts are situational at best.
Carnivore: I see what you mean about throwing out ftilt after spaced aerial or crossup to catch out of shield. I've experimented with the same idea quite a bit. It doesn't work well against good players the way you're envisioning it. If they continue to shield when you throw out your ftilt, you're stuck with 18 frames of wind-down lag (ftilt is 29 frames, hits frames 9-11), which is plenty of time to WD out and punish appropriately. On the other hand, if you hit it, they need to be at some sweet spot of mid percent where you get a knockdown for a tech chase situation/ missed tech punish so your expected value will be generally quite low if not negative. Keep them honest in shield with grabs and spaced aerials.