You're not wrong. HG used the last script Adams wrote with a few tweaks from his notes but the film still took about 4 years. Plenty of time for tinkering that sadly Adams couldn't oversee and guide. (If the studio let him)
Mortal Engines, I was excited for that having seen a Peter Jackson introduced preview (pre recorded video) at a London Comic Con.
I then read the book in anticipation, sadly, the movie was just OK.