As partly stated already the basic modding possibilities where also quite slim.
Models are just one of the points here, but there are a lot of other core functions, where the problem wasn't just the "userfriendlyness".
I can only speak for myself but I also started modding, but gave up when finally only half the stuff I'd planned was possible at all.
And to attract people that can reverseengineer these kind of things other hights of popularity are needed.
