I know this needs to be remedied by EA as a whole, but if you use mods, there is Shaving Tweaks that allows sims to shave everything at once.
From the mod description:
Adjusts Shaving Times: The time it takes for Sims to shave different areas is now more balanced. While the duration still depends on the amount of hair growth, shaving larger areas like legs will now take longer than shaving smaller areas like the face.
Introduces Two New Interactions: Adds "Shave Body Hair" and "Shave Body Hair to Preferred Length" interactions. Both options are designed to take the maximum amount of time, as they involve shaving the entire body (excluding facial hair). Both options are fully translated.
Optimizes Shaving Priority: Shaving now occurs at the start of a shower rather than at the end, perfect for players who want their Sims to quickly get in, shave, and get out
https://www.curseforge.com/sims4/mods/shaving-tweaks