I would say that right now positional ratings are pretty important as skills are very low for the players.
My approach is/was to put the player on the positions that I consider they suits better and try to make it their natural positions. I am somehow in the middle of this process.

I get the feeling that what you are really asking is "What is the out of position penalty?"

Just to throw numbers out there, Say a Player has 10's across the board for all relevant skills, If they play in a position where they are "adequate", would that be the same as playing in the natural position but with 9's across the board? If they played in the "if needed" position - is that the same as 8's? and if they play out of position, would that be 7's?

Or maybe each position has a value associated that is "out of 5-stars".. so even if your natural position would have you play at 2/5 stars, maybe an "out of position" position is a 1.5/5 stars and therefore the relative penalty is very little. But when the natural position reaches 4/5 stars.. even the "adequate" position might only be a 2/5 stars, which would likely be a much larger penalty than a 2 star playing out of position, if the position played was 1.5/5 stars.

consensus has generally been, use players based on skill types and let them adapt their natural position over time.
the strong teams you've seen have been using these players for a couple of months now out of position and have now adapted.