The Portuguese head coach has been in charge of the Manchester United side over the past two seasons.
The Red Devils finished in sixth place in the Premier League table but won the EFL Cup and the Europa League last term.
Manchester United looked to improve with the addition of proven Premier League striker Romelu Lukaku in a £75m deal last summer.
The Red Devils have been unable to rival derby rivals Manchester City in what proved to be a one-sided title race.
The Citizens finished 19 points ahead of the 20-time English champions to highlight the gap between the city rivals.
Manchester City, Liverpool FC and Tottenham Hotspur all scored more Premier League goals than Manchester United in the current campaign.
The Red Devils can still end the season with some silverware if Manchester United beat Chelsea FC in the FA Cup final next weekend.
Former Arsenal star Merson delivered his withering verdict on Manchester United’s performances this term.
“Their neighbours are breaking all these records, playing the way they are, and then there are 70,000 people turning up at United every week sitting there and thinking: ‘What’s in the programme?'”
Mourinho told Sky Sports.
“It has not been entertaining, and it has been The Mourinho Way.
“Mourinho has done this at Chelsea. I watched them play against a second-string Huddersfield team, 2-0 up. I was thinking: ‘Go and score, five, six, seven.’
“The last time they scored five goals in a league game was Sir Alex Ferguson’s last league game when they drew 5-5 with West Brom. Tottenham, Liverpool, Man City have all scored five goals in a league game, even more than that.
“The way it looked to me at the start of the season, is that Mourinho was playing to draw with all the big boys and beat all of the lesser teams.
“They parked the bus at Liverpool, drew with them, then went to Huddersfield and lost. That’s it, behind the eight ball, and it was catch-up from them.
“City just went further away. The way they lost at Old Trafford against City, they just parked the bus. It was like they were saying: ‘We can’t win.'”
Manchester United were 1-0 winners against Watford in their final Premier League game of the 2017-18 season.
The Red Devils signed Alexis Sanchez from Arsenal in the January transfer window.
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