Agreed. I also like a simple rule rather than a Luck pool. To that end:
Luck: You can give fate a nudge to turn a failure to success. When rolling any d20, add or subtract half your luck modifier (rounded up) to the roll, to a minimum of 1 and maximum of 20. Critical successes and failures are unaffected by this, and this modifier doesn't change a dice roll into a critical success or failure.
So if you have a score of 20 and modifier of +5, you add +3 to any roll below 18 and above 1 before other modifiers. In this instance, a roll of 17, 18, 19 and 20 are counted as 20, but only a roll of 20 is critical. A roll of 2 is counted as a 5, but 1 is still a critical failure.
Likewise, if you have a Luck of 8 and modifier of -1, you subtract -1 from all rolls. A 20 is still a critical success, but everything else is slightly worse.
This stops a lucky player being able to beat a proficient one most of the time, while an unlucky player is hindered but not unplayable or at the whim of a DM. It feels a little 3.5y to be adding extra numbers, but Lck 10-11 is an opt-out if you're wanting to simplify. I'm sure there's some point buy cheese (a Luck of 6 has the same penalty as 9) that'd need balancing, but this is the easiest rule for Luck I could come up with (aside from FNVs blanket skill bump and insane crit boost)