I honestly don't understand why anyone is surprised by this, or why it makes them have a negative opinion of Bethesda Game Studios.
I understood when they announced that TES VI was in development that it wasn't in active development at this time, but that the announcement was to quell the fanbase who thought TES had been entirely abandoned.
Skyrim took 3 years, Fallout 4 took 4 years, Fallout 76 took 3 years (but wasn't a mainline game), and Starfield took 5 years, which is the longest development time for mainline games by... one year, the horror, and it's an entirely new IP with space systems that I'm sure took additional time to develop engine-specific features to support. I anticipate TES VI will be a larger and more ambitious game than Skyrim and will be influenced by how they've developed Fallout 4 and Starfield, so seeing it release in 2028 with a 5 year dev time vs. Skyrim's 3 seems entirely reasonable.