Perhaps I don't understand the definition of platoon in this case, but if you mean that they use a group of players at a position and rotate them for rest or in specific situations, then I say yes it is still prevalent-more so than true two way players who rarely leave the field. For example, at Westfield that process seems to happen more on the defensive side of the ball, with maybe 4 DL for 3 DL positions, 4-5 LB for 3 positions, and 5-6 S/CB for the 4 secondary positions. They also use up to 5 different WR for various situations. That said, i would say the starters in each of those position groups usually get the vast majority of snaps until the game is in hand or the subs come in for the last 1-2 series. As you would expect, a lot also depends on the opponent whether or not this happens more or less.
I will add that quality depth has certainly diminished in the past decade or so, IMO. Some teams still have quality depth but not nearly as many as in the past. Overall team numbers are generally shrinking too (that has been discussed on these boards before). My observations are only anecdotal but that is my impression. That alone does reduce the chance that a team platoons and increases the chances of two way players.