Lightness, once it is better than PSR, is not too much of a problem to compensate for. But key SHAPE and lack of 'wobble' or bounce CAN make quite a difference to your playing.

Shape makes a big difference in that some synth keybeds have smallish black keys compared to a piano, some even have shorter white keys too... Shape also effects ease of doing smears and glisses if you play a lot of organ style. Keys with sharp corners and edges, and piano shaped white keys, with the little overhang that real piano keys have, can make palm smears much more difficult, your hand can get caught up on the corners.

And then lack of 'wobble' or any sideways play in the key really effects these smear tactics (!), and gives a clue to quality of construction, and likeliness of durability problems.

Finally, key 'bounce', or the tendency to repeat a note if the note is 'flicked' (such as a grace note) can be a problem. Many makers forget the key needs damping well at the TOP of the travel as well as the bottom!

If your skill level is high enough, all of these things CAN make a difference in how well you can actually play. Sure, you CAN sit down at just about anything with black and white so-called 'keys', and bang out a tune. But don't let anyone persuade you that it makes NO difference. For the better players, or those aspiring to improve, don't discount how well the action works as a factor in how well you can play... Ask any pianist, and the action, and how well it is regulated in a piano, is JUST as important as how in tune it is..!

Why should WE have any lower standards? You don't actually PLAY an arranger. You play it's KEYBED. It is where the 'rubber meets the road'. Don't dismiss it's importance...