Earlier this month, the prolific director Katie Mitchell announced her retirement from opera because she found it generally too misogynistic and/or racist. She has often tackled this problem by introducing new aspects into her controversial productions which install a feminist viewpoint. Her latest production of The Makropulos Case for the Royal Opera has elements that would surely have shocked its composer, Leos Janacek, who based his libretto on a play by Karel Čapek.

The plot begins with a group of lawyers trying to resolve an inheritance battle that has been going on for a century. No will has ever been found but they are helped by a mysterious opera singer, Emilia Marty, whose inexplicable knowledge of the past includes the location of the will. It gradually emerges that Marty is 337 years old, thanks to having been given an elixir of life . Over the passing centuries, she had taken on the persona of various leading opera singers, all with the initials E.M. beginning as Elina Makropulos.

The plot is complicated enough but Mitchell’s production makes it far more difficult to grasp by turning the opera into a multimedia feminist tract. At the start, we see the stage split into two rooms, one containing the bickering lawyers while the other has Emilia Marty conducting a lesbian affair with her talented young soprano friend Krista.

Meanwhile, a third source view for our attention in the form of a video projected above the two rooms and as the action goes on, we are also treated to a barrage of text messages sent to each other by these characters. And of course we have to cope with all these distractions while trying to read the surtitles as the opera is performed in Janacek’s native language of Czech.

Other changes imposed by Mitchell including adding another 100 years to Marty’s age, making her now 437 instead of 337, possibly because the opera was written exactly 100 years ago, and having Krista safely tucking away the elixir of life formula when Marty gives it to her at the end, when in Janacek’s version she burns it in a candle flame.

After all this criticism, however, I’m relieved to move on to some of the strengths of this production. Lithuanian soprano Ausrine Stundyte was outstanding in the hugely demanding role of Emilia Marty which she sang with great beauty and power. As Janacek’s complex music grew in intensity, she seemed to increase in strength, matching the musical requirements all the way.

American soprano Heather Engebretson was delightful as her lover/protege Krista bringing a glorious voice to the role and convincingly acting the part of someone much younger than the singer’s 35 years. With experienced singers such as Peter Hoare, Alan Oke, Sean Panikar and Jeremy White in the male roles, the casting was perfect and they surmounted all the difficulties this production threw in their way.

Perhaps best of all, however, was the inspired performance of the Orchestra of the Royal Opera House who demonstrated throughout the great power of Janacek’s music. The Czech conductor Jakub Hrusa has a profound understanding of music from his homeland and he communicated this brilliantly to the orchestra.

My overall verdict, however, has sadly been dragged down by my views on this production. I have always felt that an opera director’s first priority should be to respect the ideas of the composer and librettist. I dare not even wonder what Janacek would have made of this one.

• The Makropulos Case will be performed at the Royal Opera House on various dates until November 21. Box Office and details via rbo.org.uk or 020 7304 4000