Beginner endgame question: Can anyone explain the positional ideas in this boring endgame… Why is g3 such a big blunder in this position?

I’m white and I assessed that I’m a fair bit better this position: Extra pawn, his bishop has an open board but not a lot to attack right now, while my knight is centralised (and near his king) and my rook is more active. I’ve got 3 v 1 on the queen side; he’s got 3 v 2 on the kingside.

So I figure: preserve my advantages & simplify, my rook’s active, make it more active. Trade so my extra pawn is more felt. So I played g3 (I.e g3, bxg3, rf7… then he protects his pawn somehow, ra7 and I go after his pawn)… allll gravy?

But the computer says g3 is a huge blunder. +0.5; while other moves are +5 or more??

  • Nb3: +5 (I get it attacks the pawn but I go after it anyway with g3, no?)

  • a4: +5 cause it fixes the weakness?

  • literally any other pawn move is +4 ish… and they mostly seem to do nothing.

I know this so kind of an innocuous position; but I feel like I thought about this conceptually and came up with the worst possible move. So I’d like to know how I’d (conceptually) come up with a better move in future.

I’m too stupid to understand the mistake. Can anyone explain?

Is it because 2 vs is better/faster for him than 3vs2? Is it that his king can go or my pawn (I thought I could just push it/trade it).

This was a 5+3 game but the middle game played went very fast so I had >5 minutes here so I had time to think. Feel like I should’ve come up with a better move.

Hope this question wasn’t too specific; and that the answers might be generally useful to other beginners

I’m white and I assessed that I’m a fair bit better this position: Extra pawn, his bishop has an open board but not a lot to attack right now, while my knight is centralised (and near his king) and my rook is more active. I’ve got 3 v 1 on the queen side; he’s got 3 v 2 on the kingside.

So I figure: preserve my advantages & simplify, my rook’s active, make it more active. Trade so my extra pawn is more felt. So I played g3 (I.e g3, bxg3, rf7… then he protects his pawn somehow, ra7 and I go after his pawn)… allll gravy?

But the computer says g3 is a huge blunder. +0.5; while other moves are +5 or more??

  • Nb3: +5 (I get it attacks the pawn but I go after it anyway with g3, no?)

  • a4: +5 cause it fixes the weakness?

  • literally any other pawn move is +4 ish… and they mostly seem to do nothing.

I know this so kind of an innocuous position; but I feel like I thought about this conceptually and came up with the worst possible move. So I’d like to know how I’d (conceptually) come up with a better move in future.

I’m too stupid to understand the mistake. Can anyone explain?

Is it because 2 vs is better/faster for him than 3vs2? Is it that his king can go or my pawn (I thought I could just push it/trade it).

This was a 5+3 game but the middle game played went very fast so I had >5 minutes here so I had time to think. Feel like I should’ve come up with a better move.

Hope this question wasn’t too specific; and that the answers might be generally useful to other beginners