For me there is no comparison between Neo Online and LOTRO/Mabinogi. Sure, it's nice, but graphic-wise, the latter 2 are much better.

In LOTRO you will need to pay at some point, as there are massive restrictions to non paying members.
I didn't look at Mabinogi's cash shop, but you don't necessarily need to do dungeons and grind to have a good time. There are a bunch of professions that you can develop which do not include fighting. For example you can just mine, clip sheep etc and craft gears, or even chill in town and play a guitar and set a stall in front of you where people can "throw" you money lol. I actually did that for like 20 minutes and several people gave me money