Linesmen should be obsolete at this point, just like the goal-line ref. A singular on pitch ref with less ego, less responsibility, should be fit enough to cover the entire pitch for a game and concentrate on the hardest calls like 50-50 duels and keeping a consistent line every game. That should be their primary focus. VAR should be automated as much as possible. Actual bodies in the VAR room should review situations quickly, based on a blue print. Only way to make the game more fair and more consistent.
It seems every ref has their own interpretation, based on different circumstances and largely disagree on how the game should be played. I'd say that shouldn't be up to them, they should follow a set of principles. You have the rulebook, then you need to have the book on how to actually apply them. At the moment we don't and refs are asked to do different things each week. Impossible job. It should be simpler for all parties, with the right system in place, but VAR at the moment is like trying to build utopia on top of a volcano.