Could go either way.
WW2 is certainly butterflied, isn't it? I'm not even sure WW1 would look the way it did IOTL. Certainly some major war was likely, given the combination of nationalism, imperialism, modern state administration, industrial military capacities and the various anachronistic political entities trying to grapple with all this, along with German unification. But I'd say without Marxism, WW1 looks a lot different and not only from 1917 onwards. Who knows how all those political Elements filling what IOTL was the space of Marxism would have altered political events and decisions in France, Germany, Austria-Hungary etc.
I'm not so sure that WW2 wouldn't happen.
The underlying social pressures that led to WW1 seem to be intact - and whilst Marx isn't around, all that would mean is that Russia either doesn't leave the war, or engages in a civil war under different terms.
Perhaps a peace deal with Russia involved is less brutal, under a situation that leads to the Tsar being able to moderate internal problems, and wanting to prevent those same pressures destroy Germany, and cause a radical state to emerge to make their life horrid.
But overall, whilst the Post-WW1 theories may change, I'm not entirely convinced that a follow-up war isn't going to happen, short of German Jainism becoming the dominant school of thought in Germany after WW1.
Even if we assume that WW1 has different triggers, I doubt we're going to see Germany and France on the same side - and as a result, one or the other will be dealt harsh terms because at the time the consequences of those harsh terms weren't expected, or if they were, those expectations were ignored. Leading to at least one radical economic climate that leads to a radical state.