Twice now I've started writing a lengthy post about this and deleted them
When people talk about a game being easy or difficult they often are not talking about the same metric of what makes it so. Is the pace too slow or too fast? Is it grindy? Is it tedious? Are the mechanics convoluted? Is it heavily group dependent? Does it take people skills with a high level of being able to coordinate with others to play? Is it as simple as not being competent with the play style such as action vs tab targeting? Are the materials needed to set out a character placed or locked behind aspects of the game many players cannot readily pass?
When I say a game is easy or difficult what I mean by that is how reasonable is it for the average player to excel at the game. And, by excel, what I mean is attain a point in the game with a character where the player can see and do much of the content and acquire much of the resources to do so. Not world first or chart topping levels of excelling, but being able to at least get a group, enter, and survive doing higher end content levels of excelling.
In about 18 years of playing these games I've had the opportunity to test many of them and have long since lost track of how many trials I've played. I've spent 90+ days in 2 dozen or more of them. Of all of those games, CoH is still by far my favorite, but not because the game was a challenge to me. It was my favorite because of the people who I played it with, the people who made it, and because I liked the setting. And I would say that, even though CoH was largely people hanging out while collecting 50s, it still set the bar higher for the average player to excel at than CO.
CO is an easy game. I don't say that because I got used to how it plays. I say that because when compared to all of the other MMOs I've played over the years, it is easy. The bar is set very low in CO in most ways unless I compare it specifically to games like Trove or Horizons. It's certainly takes less to excel at than NW and much less than STO, which would be the closest, most proper comparisons I would think.
Again, that's not a bad thing. Sometimes just smashing things is fun all by itself. CO was good at that.
As a bonus, CO had one of the better MMO RP experiences I've encountered. After a while it was one of the main reasons I kept coming back. That is a testament to the people playing the game, though, not the game itself.