The problem is that you are thinking the same way people back the early 20th century were on IC engines relative to horses. They would say
"I would much rather have a lighter, faster horse with just a traditional heart" <---substitution is a beautiful thing
I'm all for research and delving into other means of doing stuff in order to sus out what works. If it turns out that electrics, hybrids, or whatever the balls else don't work out, so be it. It's a challenge and that's what makes it a beautiful thing.
Porsche isn't trying to develop a hybrid for the purpose of just fuel economy. The problem we have is that electric drivetrains are being touted as the end all, be-all of fuel economy by the masses (including you, judging by your post) when other applications are there, with the case of the 918 (and 908 HDi FAP and the R10 and the R15 etc from Audi) being for the purpose of handling/powertrain performance for the purpose of speed.
Felix Wankel was told his shit was weak and would never work out. To this day, Mazda is still keeping his tech alive (they are in fact developping a new Magic Spinning Doritos application). In his case, I can argue it was and should be a losing battle but it was a battle he fought and time proved it doesn't work as well as the Otto, Atkinson or Diesel cycle
My point? let Porsche and others explore all the possibilities and see what comes of it. Hybrids are still young and as humans, we have the obligation to let it prove itself before we let time pass judgement
Something about causation and correlation