OK, so let's use D&D 5e (as that is the one from that list I know the best): In that game they are about 500% more important than in Rolemaster, a not-so-great attribute for your main abilities is really harmful as it makes all the bonuses and save numbers based upon it to be significantly lower. With "Bounded Accuracy" meaning your skill modifier has a range of 5 (+2 to +6), which is the same range as attribute mods (+1 to +5), means that your attribute mods are equal to that of your skill mod.
In RM - especially RMFRP - your attribute mods go to +10 (not including racial mods) where your skill bonuses are +50 at 10 ranks (assuming both Category and Skill were developed equally), so they will ultimately be outshine your skill mods, especially since they can continue to be developed and the bonus increased. Though at low levels good stats do give a nice bump in capability. Now, the game does let you know which attributes are important for your profession so you know where to assign your good numbers so you are unlikely to have bad mods for those. You do want to make note of any racial mods and how they can affect certain professions.
I highly recommend using the Talent & Flaw system out of Character Law if you are concerned with characters not being capable enough - but I also believe differently than most RM people about what "capable" means. As far as I am concerned, being able to succeed half the time at a medium maneuver is a low capability. I like to think of it this way: If I messed up half of the time work threw me a curveball, I would not be able to keep my job. So, for me, baseline capability doesn't start until they hit +70 or so, when they can handle medium maneuvers most of the time. You can, of course, be the judge of what you want it to be.