Gabriel Jesus appeared to put Man City on their way early on, as he scored just four minutes into the contest to give the reigning Premier League champions a 1-0 lead.
But the game remained a struggle for Man City, with that Jesus strike the only goal in a tight affair.
While the result sends Man City to the tournament final in May and keeps their quadruple hopes alive, former Citizen Toure found himself unimpressed with the outing and suspects Pep Guardiola feels similarly.
Toure even went as far as to speculate a better team might well have ended Man City’s FA Cup hopes.
“I think for [Guardiola] it’s not just about the result,” Toure told BBC Sport. “It’s about everything.”
“I was a little bit concerned because City lacked energy. They were sloppy. After the first goal we saw more of Brighton than we did of City. Maybe if they had faced a better team they would be out.”
Man City’s attention will now shift back to the Champions League, where for the second year in a row, they will face Premier League foes in the quarter-final.
Last season saw Guardiola's charges lose their quarter-final first leg 3-0 at Anfield to Liverpool, en route to a 5-1 aggregate defeat and exit from the competition.
This season Man City take on Tottenham at Spurs’ new stadium on Tuesday in the first leg, with the squad looking to avoid a similar early hole as they suffered last term.
And following the performance against Brighton, Toure sees the match as a big test for Man City against a team that has a much higher level than the Seagulls.
“They are still on their game and looking forward,” Toure added. “They have an important game on Tuesday [against Tottenham Hotspur in the Champions League] against a better quality of player.
"It is going to be a massive game.”