I’m not sure that the components couldn’t handle the range...at some point. It may have been able to when the derailer was new but the derailer could have worn out over the years. It would be worth putting a new derailer on and see if it works better. Here’s what my bike drivetrain looks like in various gears.
46x11
20x11. The chain is a little slack but I wouldn’t never use that gear anyway.
20x36. That’s a 15” gear. In terms of “development” or the distance the bike move with each pedal revolution, that’s 1.2m (a bit over 6’). It’s 4 mph at 90rpm. I may not be able to go very fast in that gear but I can ride up most anything...slowly...but I’m still pedaling.
36x36
46x36. This is the only fly in the ointment. The derailer is stretched to it’s limit but I would never, ever put the bike in this gear. I would shift down to the middle range long before I even got close to this situation.
By the way, your gearing isn’t quite like mine.
Here’s what your’s looks like with a 20 tooth inner. The calculator won’t allow for an 18 tooth inner but if you do the math, the 18x30 is a 16” gear which is just a little higher than my 15” gear. Your high is also a little lower than mine. Looking at the gearing, it is kind of smart as well. It what is called a “cross over” gear...not to be confused with cross chaining”. The shift from the outer ring to the middle ring is about the same step as downshifting the rear. For example look at the 40x24 gear. It’s 65” gear. Downshifting to the 40x28 gear goes down to a 54” gear. Down shifting on the front to the 38x20 gear is a 51” gear. Assuming that you start in the 30x30 gear, you would shift the bike in the rear to the middle gear (20 or 17) and then “cross over” to the outer ring and continue up the cluster to the high gear. Just reverse it to go back down.
The 18 tooth ring is used as a bailout when the hill in front of you just keeps going towards the clouds. When you hit the top of the hill, just shift up to the middle ring and start upshifting. It’s actually a really good shift pattern.