Craig Gilroy managed two tries in reply but Leinster maintained their unbeaten home record for the league season to end Ulster's season.
The Ulstermen have finished fourth in each of the last three seasons and have not reached the showpiece final since they topped the league in the 2012-13 season.
But Kiss has moved to reassure fans that the team will continue to improve over the coming years to a point where they can challenge for silverware again.
"Our roster will be undoubtedly stronger next year with the new players coming in, some young and also strong foreign talent," he said.
"You need a blend of both. We will be stronger next year and we will be even stronger the year after that. It's not built overnight.
"We've a good Academy system and we're working hard to make sure we can improve that and bring them through.
"We'll see some guys step up to the plate next season because we need to broaden and deepen.
"You need the capacity to build that through financial resources and good coaching. Hopefully we are putting together a programme to deliver that."
An away semi-finalist is yet to progress to the Guinness PRO12 final after two more home wins for Leinster and Connacht this weekend.
And Kiss was quick to look at the bigger picture where lost bonus points meant the side had to travel to the RDS rather than welcoming opposition to the Kingspan at the semi-final stage.
"Not beating Munster, not getting points from one or two games, that was critical," he added.
"It refers back to that mental attitude of not allowing games to slip away.
"Even if you've lost them, Cardiff was a big one. If we had got just one more point out of that, it would have made a difference.
"Get another point somewhere else, it makes a difference."
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