He won't assist more, and more complete is a weird term because there's no prizes for being an all round player as this isn't 5 a side where everyone has to do everything. The reason Messi doesn't run non-stop is because he is 32 and has played close to 900 games, he has to conserve his energy or this Barcelona team won't win anything. The reason he doesn't press and tackle, is because when he did, when Pep first arrived, he got injured and he's too important to allow that.
Messi is the best goalscorer, assister, passer, dribbler and free kick taker in the world and there's a decade worth of performances, statistics and trophies to back it up. He will go down as one of the 3 best players to play the game and I don't know why people try to compare other players to him.
Just enjoy Kev's performances on their own, and if he has another 20 games like today in the right games, we might win everything and he'll get a ballon d'or, partly because people are bored of giving them to Messi.