No such thing as a 'forwards' or 'backwards' formation, but you have to ensure the players you have suit the formation and gets the best out of them. My dad knew a thing or 2 about the game and would always say you don't start with a formation and fit players in, you look at your players and work out the best formation for them. I don't really see why anything should be different these days compared to 30 or 40 years ago, because the game hasn't changed. It's still 11 v 11. The dimensions of the pitch haven't changed and the rules of the game are the same, bar from some very small tweaks.
Case in point: Why did Ollie's 4-3-3 work? Because the full backs naturally enjoyed going forward and providing width. Because the midfield 3 of Southern, Vaughan and Adam totally complimented each other to create perfect balance and the front 3 - whoever played there - generally had players like GTF/Brett who understood the 'inside forward role properly to offer maximum fluidity and movement. The forward players probably had the most to learn in the system, but for everyone else the system was set up to let them play to their strengths.
Compare with the current situation and you have a right wing back who is left footed and thrives in playing in the oppositions half and by running into space behind the back 4 - which is generally not where a wing back tends to find themselves without leaving huge amounts of space for the opposition to operate in. We also have a left wing back who is totally right footed, much prefers the 'industrial' side of the game and isn't particularly good on the ball for someone who is likely to receive a lot of the ball.
I'm not sure I need a coaching badge or badges to work out what's going to happen here...