The Belgium international was United's hero on Tuesday night as his 91st minute winner booked his side's place in the last 16 of the Champions League.
Young Boys had frustrated United throughout, with Fellaini and his team-mates struggling to break down the rigid Swiss defence.
Despite the later winner, Fellaini was unhappy with the crowd and lack of support. "Of course it's frustrating," Fellaini told 'Sky Sports'.
"But that's football. They come, they pay for their tickets and they want to see good football.
"But today the spirit was good, and we have to look forward with a lot of hunger. Criticism is part of football, but we have to work. We are a team, we are together and we give everything. Together we have to move forward and take the points.
"We played positive football from the first minute and wanted to score. I think everyone can see that. We gave everything to score the goal and I think we have to continue that way.
"We had a lot of chances - we played forward. I think we have to keep this spirit and look forward. We play positive, score goals and show supporters how we want to make them happy."