McGahan's men were beaten 16-6 in Dublin on Saturday night as the hosts booked a Grand Final tie with the Ospreys at the RDS on May 29.
The defending champions played their part in a ferocious encounter but could only manage two penalties from outside-half Ronan O'Gara as Leinster closed the door on every single attacking opportunity.
"I thought their defence was excellent again and I thought their set-piece gave them a great platform as well," said a dejected but typically honest McGahan.
"We battled manfully. There were a lot of players without a lot of training time underneath their belts, so to fight our way to the end and be beaten by one try to nil is disappointing.
"I thought we created a number of opportunities but their scramble defence nullified us.
"We didn't take enough opportunities. We had three turnovers in the first 15 minutes inside their 22 and, when you're starting a game away from home into the wind, we really needed to make sure we got points early.
"They fought hard at the tackle, really slowed down our ball and that gave them a great opportunity to reload in defence and make sure that they kept coming at us."
Unfortunately for Munster, Saturday's defeat was their second semi-final loss in just two weeks.
The double European Champions saw their Heineken Cup dreams ended in Biarritz on May 2 before their bitter rivals ensured McGahan and co ended the season without any silverware.
On neither occasion were Munster beaten by comfortable margins but McGahan admits that can't hide the frustrations of defeat for a side that many critics are harshly suggesting is coming to the end of the road.
"We've just come out of two semi-finals losing 18-7 and 16-6, so I think we're not too far off the mark," added McGahan.
"We're disappointed. It's the end of the season for us. There's no more next week - there's no more final.
"There's always going to be questions about the age profile of the side, that's inevitable, that's always going to be there. I think it's been there for a few years and we keep rebounding and keep competing for trophies at the top end of the season. So, we're there again, but alas a step too far.
"There's no doubt there are players getting to the end of their careers, that's been well documented - 12 months and 24 months - for the majority of them, so we need to keep moving on. That's a challenge for a new season."
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland