I can't read the linked article, but in general, any technology constantly tries to push the limits. Jet engines are a very mature technology, so there are less

I can't read the linked article, but in general, any technology constantly tries to push the limits. Jet engines are a very mature technology, so there are less improvements by just improving the general design. The next step is optimizing each part, e.g. by selecting new materials to make the parts from. This usually means a large performance leap - new materials can mean a way better performance - but also a time where there are struggles to make a new material working reliably. With time and experience, reliability grows and progress slows down till the next large step, which might reduce the reliability somewhat. On top of those things, I heard stories that GE for example laid off a large amount of their experienced engineers. This certainly increases the risks with new designs.