While it's certainly possible to play Bach too romantically, it's worth remembering that the great majority of what Bach wrote was vocal music, in which it is perfectly possible to shape phrases dynamically. I have no way of knowing, of course, but I rather doubt that Bach considered the inability to shape phrases dynamically on a harpsichord a positive virtue. One can create the illusion of dynamic shaping on a harpsichord by ornamentation, subtle changes in articulation, changes in textural density, and all that is wonderful, but I doubt Bach would have scorned the dynamic flexibility of a modern piano any more than he did that of the human voice or the violin.
Fair points to ponder, certainly. I think, though, that even though Bach was a paid composer (paid servant?) that he still wrote for instruments that he not only knew, but also happened to like/love - not those that he saw as limited or inadequate in some way.
I mean, if you're a composer that doesn't like tuba, you tend not to write a tuba concerto, right?

I can't say what Bach would think of the modern piano, or the way his music is played today. I think it's worth being aware, though, that the modern piano was not anything like the instruments for which he actually did write his music. I also think it's worth being aware that the musical "language" in the baroque period, and before, was notably different than that with which we are most familiar today - and that this language was not necessary "inferior" to that which we are so used to and like today - it was just very DIFFERENT.
If we grow up learning and speaking English we tend to think that Russian, say, is maybe more difficult to learn, and to understand, and maybe we even think it is a "harsh" language, or whatever. If we learn it, we will speak with an accent that favors our native tongue. That doesn't mean Russian is an inferior language - just different, and not what we are used to.
By the same token, the modern piano with its equal temperament and the way we tend to play it in a more romantic fashion than anything else is what we are used to, and therefore what we tend to like. Doesn't meant that the language of earlier music or instruments is inferior - just different.
If someone from 1650 lept into the future and was faced with a modern piano who knows what they'd think, but I'd imagine they'd find the instrument foreign and less pleasing than what THEY know - instruments like harsichord with UNequal temperament that can be heard like laser beams on this instrument (part of this earlier "language", in my opinion).
To each his own, of course, but I, personally, find enlightenment in awareness of earlier styles, language, tuning, and most of all - instruments. I do not find such things inadequate in any way - just different - and incredibly beautiful - again, in their own way. The modern piano is hardly a perfect instrument. What it gains in one place, it loses in another place. A lot of people aren't aware of these 'losses'.
For what it's worth.

JH