I think as an idea it's great. I also think they implemented it in the literal worst way they could have.
Having some form of Power-Up/Prestige program is perfectly fine with me. But limiting it to online only is a terrible call. The generic +3 that was featured this year wasn't really that amazing for most cards. Some crossed certain thresholds or had various effects like that, but overall it just wasn't enough to really move the needle that much. It was more of a "badge of honor" type thing for those that grinded online a lot. Which, fair play, as rewarding people for playing the game is sensible.
But I still see no reason why it can't be a combined effort between online and offline. As Chuck mentioned above, the way they developed the various programs with a mix of online and offline missions is the way to go. I didn't really touch Ranked all year because I just didn't enjoy how the game played online this year. I spent a fair amount in Events, though, and usually got annoyed by people trying to boost before the gameplay annoyed me. These types of things shouldn't really affect the way people play.
So if people can earn them offline, that's even better. For those that don't want to play online at all, they can still earn something new and it will keep them engaged with the game. Even if there IS an online requirement for ABs or IP or something, with a loose requirement like that it should deter a lot of people from boosting. Instead of being able to go in and attempt to boost for Hits or XBH or K's or whatever, if you just need x Plate Appearances then you're much more likely to play. If you need 211 IP with a pitcher, you're much more likely to actually play.