He actually comments on Luke's lack of practical ability a few times throughout different interviews. The one I was thinking of was this:
I mean, on a basic level at this point he’s so much better trained than Luke could ever be. It’s just an interesting take on what are all these other people that have the Force doing? And how do we not have that interfere with the blinding light, the New Hope that Luke Skywalker becomes? Luke’s mission in the Force is very specific. Learn to be selfless. Selfless enough to save your Father. To realize that you can forgive and redeem. And that’s a bit different than where we’re going with Ezra and Kanan for sure.
It's worth noting that this was referring to Kanan, though. He also mentions in earlier interviews that he didn't think Luke would be a match for any of the Clone Wars era Jedi Masters either, but I'm having a hard time finding it. Make sure to ask DT for it next time he shows up.
If you look through the interviews where Luke is brought up in this context, though, it's pretty clear that Filoni believes Luke to be inferior to other Jedi in terms of fighting ability. Instead he emphasizes his outlook and attitude and so on so forth as his important qualities.
Whether or not I find Filoni's position on the matter stupid or not is pretty irrelevant. He's someone who works closely with the Story Group, the guys that lay down the law on canon. Ergo the odds are that his comments regarding both Grievous and Luke are aligned with the canon.
Which, as I said before, is still totally irrelevant because the topic is DE Luke, who falls under the Legends banner.
1. The Count should take this due to being more skilled than Cade, Dooku wouldn't have much difficulty beating Talon, Nihl, and the other people from Cade's era and would perform better against Krayt in a duel. The force round favors either, but Dooku should win due to being more skilled
2. Luke should take this with mid difficulty, as of DE he should logically be beyond his father and is just more powerful overall.
3. ExarDurron ragdolls
4. Geth chokes him out
5. Dooku stomps. Traya is inferior in just about every regard
6. Dooku handily
7. Wins with difficulty. Ulic can defend himself from lightning, and can pressure him in a duel but is just slightly inferior in the force/skill
8. Honestly depends. Hindered Mustafar Anakin could lose or win if he just pounds Dooku's defense. I'm not sure
9. Not sure
10. Krayt in a decent fight