Anyone who's ever played fortepianos (or modern reproductions) of the Classical era, or the early grands of Chopin's time (Pleyels and Erards) will know that not only are their actions lighter than modern pianos (upright or grand) but their key travel is also shallower...
Likewise, the cascades of arpeggios that make Schubert so wonderful were written for instruments where the cascades were created by rolling the hand and wrist, not by striking each individual key, as we do in a modern piano. This not only because of the action set up, but because the sustain of these instruments was quite short...one had to play many closely spaced notes to create the "impression" of sustain, when the sustain effect was called for.
From the get-go, playing this music on a modern piano, despite the fact that it is called "piano literature", is a serious "interpretation" and "re-invention" of the music.
Fine...so be it. The modern piano has much to offer in terms of sustain that can benefit this music as an "interpretation" of the composer's intent is(if one can ever claim to know what this)...and be quite beautiful in it own right.
However, this music is not the music of "power", but rather it is the music of lyricism.
Power was not even part of the equation until the very late romantics who, as it were, were the first superstars performing in larger venues. The concept of their music needed to fit the intended large venues,and required power.
This leaves the modern piano in a position where it is asked to do the impossible. It is asked to be all things to all music in all venues. Even when its only used in a home setting or small chamber setting, as a huge percentage of pianos are, it is asked to pretend its a 9 ft piano projecting to the back of symphony hall over a symphony Orchestra.
...sadly, this often leaves lyricism to languish.
So in my view, as is so often the case, the issue really is one of accurately defining the problem, before offering the solution. In terms of defining an action inertia, the first step is to ask one's self what level of inertia turns on one's muse.
What level of inertia draws you into your piano and your preferred music? What level of inertia suites the particular music you love to play?...as most of us have a smaller subset of the literature that really speaks to us. What level of inertia suites your body musculature? What level of inertia makes it possible for you to negotiate the technique requirements of your preferred literature? ...a biggy...what level of action inertia makes it possible for your piano's tone to sound how you wished it sounded, as hammer mass( and its inertial consequences) has serious tonal implications, as Del has described so well.
These are the priority questions, at least in my opinion, because if they are ignored the joy of music making often recedes and the playing gradually stops.
Unfortunately though, they are often not the first questions one asks. Instead they are replaced with; Will the feel of this action effect my meteoric rise to stardom? Or,will I be able to play other instruments on the extremely rare occasion that I do this? Or...some other concern that is not necessarily the voice of one's muse speaking but some imposed opinion or concern.
Imposed opinions may have a place sometimes for professional performing concert pianists, but lets be real...these people are outliers. They must develop musculatures that many of us don't have, will never have, and simply aren't needed for us to enjoy playing our own music for the shear pleasure of it. Or put another way, the high inertia built into concerto instruments do not complement the end use tonal requirements of 99.99% of the pianos in the world.
...But can we turn the clock back?
Not turn the clock back, but realize that the piano action's inertia and tone can and should be be targeted to suite musical requirements and customized to suite different personal tastes.