People do hate this for a reason, me including.
You can't expect to buy just 70 levels, have absolutely no experience with it, the skills and the overall gameplay mechanic and how they are eficiently used n played out and expect from this to be immediately able to play the job like the most talented pro player.
Experienced longtime players get quickly an eye for level booster noobs that are just too lazy to play the game right and get to learn their job they play from scratch on to learn how to play effectively thei skill rotations, which is the most obvious thing people recognize, especially from DPS, when the damage of the group sucks, due to booster noobs in the group constantly failing at doing their skill rotations right, or because of using many or certain skills not, because of being clueless what the skill does, or when/ at which moment you should which skill, resulting in thesd kind of players obviosly dieing also more oftenly from their made mistakes or from being unable to use the right skills at the right moment.
Often you reconize such players also by being too stupid/unable to use Limit Attacks, because they rushed witgh thesec brainless boosters into the game, without even knowing at all the game's tiniest BASICS.
This is why booster noobs are disliked and have that bad reputation.
So the only advice I can give you, If you don't want to go in blind and suck ( what you most likely would end up doing) is - say no to boosters, take yourself the time to Level RDM from 50 to 80 while playing the class normally through its job quests and you will get the understanding of playing this job to suck not witg it.
You do yourself only a favor with that, as others as well too
Boosters are good/senseful only for experienced players with Alt Accounts, which want just to save themself some time, so that they don't have to go through all the stuff of the game again, that they already know from playing the job the first time on the Main Account.