The way I look at it, they need to make those areas more "modern", just for the simple fact like you said, to compare to what they've already overhauled.
Look at Evendim now. It's like Easy Street compared to Trollshaws and Misty Mountains. The leveling is easy, the pace is fast, the content is plentiful. In these older zones, the content is sparse, the leveling is almost nonexistent at times and the pace is a crawl. So to keep up with their current revamps and expectations from the newer player base, they have to revamp those areas to allow them to compete.
It's a good thing, though, because those areas weren't getting much love from anybody. As much as I love the Trollshaws, it was rare that I'd find anyone exploring that zone. Even rarer was trying to find people to help you with the group content in those zones. If you're without a kin, you're not going to get much from those zones at all.
That said, if you actually can complete the content there, man, is it rewarding. It's so beautiful traversing the Trollshaws and discovering all it's nooks and crannies. I love how the back paths are so dangerous. I have very fond memories of learning that place and it was kind of a badge of honor that I fully explored that zone. I also helped other people enjoy it as much as I could, because I wanted to share the experience.
So anywho, I'm glad it's getting revamped. As much as I love it, it's for the best. Let some people actually enjoy the area rather than skipping it.