Many opponents push back deep any backspin serves, and will often even do so against a sidespin or even topspin serve by chopping down on the ball, often right off the bounce. And so you get a predictable backspin return off your serve.
If the opponent is going to give you these slow, predictable backspin returns, then you must take advantage of it. This means starting all of these rallies off with a serve and loop, either forehand or backhand. Simply decide you are going to do it, and do it. Yes, easier said than done, but the more you do it, the easier it becomes. You don't need a lot of speed as long as you get good spin, loop the ball deep on the table, and vary the placement to the wide backhand, wide forehand, and at the opponent's elbow.
Often it's best to serve short to the middle. By serving short, it makes it difficult for the receiver to attack the serve, and so you get those predictable long push returns. By serving to the middle, you cut off the extreme angles.
You should favor your stronger side - usually the forehand, though not always - but it's better to be able to attack from both wings when necessary than give away such a free attack. Don't over-anticipate the direction of the incoming push; wait and see the actual direction as a crafty opponent might aim one way and change directions at the last second.
How important is it to attack these long backspin receives? I've seen top players coach matches where they were literally confused that they had to actually tell a player to do this since it seemed so obvious and second-nature to them.