Why should interrupts be short in a well configured system?
Not only is there no reason you can't do that. An event driven system is not uncommon. BUT. On many architectures if you are in one interrupt you cannot have another, so even a low-priority interrupt can in some systems prevent a higher priority interrupt from happening, so the general rule is to get in and out fast. Often a design approach is the interrupt comes in and does some handling, but leaves a task for the kernel or foreground task to finish, more seen with operating systems.

I believe the Cortex-M can nest interrupts, so if one comes in on top of another it gets handled. Most of the chip is not related to ARM, so there isn't any reason why the chip vendor can't put an interrupt handler in front of the Cortex-M and/or a priority handler, in addition to whatever is in the arm end of things.

Nevertheless, an interrupt-driven design needs to be designed. As with any other design, you need to do your system engineering. You need to know every possible interrupt (under normal situations, undefined instruction, etc are fatal) and how often they occur. Many will be regular periods.

You also need to know how long each interrupt takes, and schedule this such that you can ensure that all interrupts will be handled in an amount of time that meets your specification. For example, a timer-based interrupt event for something takes 50&nbsp;ms to handle normally, but there is one non-periodic random interrupt that takes 20&nbsp;ms. Is 70&nbsp;ms tolerable for either of these? Does the chip/core have a priority solution? If not, have you laid out your interrupt priorities such that you can meet timing on everything?

At the end of the day, there is little difference between all interrupts and some interrupts and some foreground with respect to the design and timing of the interrupts; you have the same problem.

So the general rule is make interrupts lean and mean and fast, but the reality is do your system engineering and know how much time you have for each or groups of them combined. It must take less than x amount of time.