I played RO1 many time ago and I can say that they are totally different games tbh. In that sense I do like some features as well as I dislike others. Many things I dislike are product of big imbalances that are being worked atm and after big update I came back since I guess the most expected changes hopefully will come soon.
Now about the main gameplay mechanics differences are:
- Your SP is way higher than RO1 and skill mp cost are lower, so you can keep using them (and at higher lvls you barely will need to refill your SP).
- Also your HP is higher, so battles in RO2 tends to last a bit longer than RO1 when fighting monsters around your lvl (at higher lvls, monsters start getting high hp pools)
- The first 50 lvls (and maybe 70, haven't started playing with my lvl 51 character yet) are mostly quest grinding rather than monster grinding to lvl up (you can go monster grinding if you want to, it's not impossible to lvl up that way)
- Classes in RO2 aren't equivalent to RO1 (can't go in depth on this). For example, Priest on RO2 can be a very good DPS class, and can act as a secondary support when a Soulmaker is in a party.
I can't think on anything else and somebody else can complement what I already said, but my best advice for you is to try the game yourself and see if you like or hate it, personally I think it's really enjoyable.