There is a reason not a single modern commercial rocket startup uses a hydrolox core, solid boosters and a hydrogen upper stage. Late staging makes it impossibl

There is a reason not a single modern commercial rocket startup uses a hydrolox core, solid boosters and a hydrogen upper stage. Late staging makes it impossible to ever develop real re-usability. The first stage engine, is very old and very expensive and slow to build. Its a gas-generator and not a very well optimized one. Solids are simply not competitive and only used by government launchers. Its an architecture that goes back to the Post-Apollo area. The believe in hydorgen fuel and solids is inspired by the Shuttle. Ariane 5 was literally design for a Shuttle clone type system. The Upper stage, while having an amazing modern engine (20 years in development), is actually just terrible in terms of structural design and is getting out-performed massively by Vulcan 5, Falcon 9 Upper stage and new entrance like Neutron. The system requires 3 different types of propulsion systems and all of them in low volume. Yeah why would that not be efficient. SpaceX on the other hand only uses two variants of the same engine. Despite re-usability that engine gets produced in high volumes. So for each $ invested in better engines, SpaceX improves its whole stack. Arianespace needs to optimize 3 radically different engine system to improve its whole stack. This partially explains why SpaceX radically out innovated Arianespace even in the same rocket generation. Go look at what the French Space agency proposed for their 'Ariane Next' design only a few years after Ariane 6 was agree on. It was basically a Falcon 9 design. Think of the Ariane 6 design like a WW1 bi-plane design evolved for use early in WW2 and we are now already going into post WW2 war jet fighters with systems like Starship/Raptor.