I personally think there is still a place in the modern game for scrums, even if just for the sake of variety. It may not be contested like it used to be or as technical as union, but it still serves a purpose and was sorely missed imo in super league the last couple of seasons.
A scrum will take 6 players from either team (7 if you include the feeder as 90% the person in the back of the scrum will pass it out nowadays as its the safest route for the ball) basically out of the game for that play and allow for a more open flowing play. More space, more gaps, unique set plays more excitement.
If you take away the scrum as was done in SL the last couple seasons and make it just a simple turn over of possesion, you essentially are just left with another standard tackle (most likely a settler drive to set up field position for later plays being the 1st tackle). Whereas if you keep scrums you have the first tackle be a potentially more exciting, open field set play. Allowing for greater play variety as opposed to a dull, old 1st play of the ball.