The improvements recommend above by @happypig make a lot of sense because no rules would need to be altered whether the game is covered or not by VAR.Before the introduction of DRS and neutral umpires there were some shocking decisions against touring sides in India and Pakistan (Javid Miandad was never out LBW at home) from local umpires.
Back to VAR, it seems to have lead to some refs/linos abdicating responsibility for tricky decisions thinking "VAR will sort it out". Couple that with the perfectly natural desire not to be shown to be wrong and officials (whether on field or at Stockley) have a subconscious bias against making a contradictory ruling or recommendation.
How to improve it ?
Make ALL decisions the Referee's call. If he isn't sure of a goal or offside then ask VAR to check. If he misses a foul or red card, so what ? Might stop players going down looking for a penalty in the hope that "VAR might give it; there's no sanction if a player does this and is thought to have simulated.
Complete separation of PGMOL on-field officials and VAR; maybe have the VAR officials drawn from overseas refs and ex players ?
Offside, get rid of the lines and make it so a player has to be clearly in front. Not just a toe or eyebrow, the whole player. If VAR cannot say he's gaining an advantage by being in front, then on-field decision stands.
Referees have to give a post match interview like managers do.