Death Stranding came out in 2019. Death Stranding 2 will come out in 2025. That's six years for two games. If these were the PS2 days Kojima would have cranked out 3 Death Stranding games by now and we'd be getting Death Stranding 3: Subsistence along with a teaser for Death Stranding 4 next year.
Remember when video game trilogies used be to a huge thing in the sixth and seventh generations? You'd typically get 3 games in about 5-7 years
See: Halo, Gears of War, Resistance, Killzone, etc
I don’t think game dev changes that much (timewise) with older graphics but same scope (maybe I’m wrong), you still have to have artist design this shit with lighting, surfaces, colors etc, it doesn’t (again, I suspect, not a dev) become that simpler/faster just because you used ue4 instead of ue5 to draw a city, for example. If you spend roughly same time, it’s probably a wash what you used.