Mass Effect 3, which is by no means a small or content-poor game, however controversial its ending, was released just two years after its predecessor. It incorporated a number of obvious mechanic/gameplay updates, engine tweaks, and QoL improvements. It even incorporated a popular multiplayer mode. All of the music, all of the voice acting, all of the motion-capping (if they did any of that) was done quickly.
Bioware could release "Mass Effect 4" with the same mechanics and systems, if the story's good enough, and people would be (extremely) happy. So what now takes them >8 years that previously took them two?
Also noteworthy: Content can't possibly be the bottleneck, as Pillars of Eternity (a Baldur's Gate-like RPG) and its sequel were released within a roughly three year period, and those games contain millions of words of content. The second game is also fully voice-acted.
For example on Infinite you had a scenario where people might not be around long enough to learn the in house tooling which was troublesome enough to cause some to want to drop what's been done and switch to Unity whiplashed around by directions set by different parts of the company and half the workers were 18 month contract workers.[1]
If you compare the credits for the Mass Effect trilogy series for example there's a good amount of people who left by the end of ME3 and fewer are still there for a ME4. Mike Laidlaw, Steve Gilmore for example. Drew Karpyshyn is lead writer on only the first two ME games. Aaryn Flynn, James Ohlen and Casey Hudson both went off to make their own studios.
[1]https://www.bloomberg.com/news/articles/2021-12-08/how-micro...
Naughty Dog released Uncharted 1-3 and the TLOU during the PS3 era so 4 games. They released Uncharted 4 and TLOU 2 during the PS4 era which is 2 games. And so far they haven't released any game during the PS5 era (not including remasters/remakes). They will likely only release 1 new game before the PS6 is released.
Lets take Starfield as another an example since its the next big studio RPG to be released. Its been in development since 2015 so basically 8 years.