There wasn't less contention and it just feels that way as we see many more slow-mo HD close decisions. In the past you didn't have as many live matches on TV, nor the tech to show it as clearly or to watch it on given HD hasn't been around forever. Offside is not always about drawing lines as there are also occasions where the ball hasn't even touched an opposing player or vice versa yet an incorrect decision was made as a linesman missed it, whereas VAR sees it without the need for lines.
The margin of error has also improved as before it could be as close as a big toe or further away such as a couple of feet, even yards as we've all seen on TV replays in the past. That's why it came about as mistakes weren't just close, they were often shocking. Even though VAR is making mistakes and some shocking, it's not to the level pre VAR when anything goes.
Like you I don't want to see a goal cancelled due to an offside of a big toe. I would like to see an offside given where there is no doubt at all, so that could mean the freeze frame shows he's offside but due to the tech they can't prove it offside. That's why the margin of error would work so that when an offside is called it is because they're 100% sure and not because the line is a pixel either side on an image that isn't the exact moment in time the ball is touched.