Jasthill raises an interesting question as to what Mahler would have done if he had lived say to 65 thus 1925. On the basis of the Sym 10 which he did complete in short score and orchestrated much of the first half of the work, there is not really a fundamental change. The Sym 10 is not shorter than his other symphonies and the style is still romantic. The main difference I hear is an almost continuous lyricism in the outer movements. Would this have survived WW1? It seems highly unlikely. It's quite possible he would have just retired as a composer like Sibelius and moved to the US.
I would also note that Germano Austrian composers even slightly younger than him like Richard Strauss and Alexander Zemlinsky never bothered much with symphonic writing after their student days. So he was increasingly alone.
I would also note that Germano Austrian composers even slightly younger than him like Richard Strauss and Alexander Zemlinsky never bothered much with symphonic writing after their student days. So he was increasingly alone.