He's already shown a top 10-15 midfielder in the world level at times during last season and this season.
As usual, you're going over the top. What I said is realistic. He's definitely a talent but has several flaws right now. His ceiling is top 10, top 5. By the way, a starting midfielder at Barca is usually in the top 15 midfielders in the world. Not always, but usually.
I don't think that he has ever shown that level, but even if he had, that is one thing which I don't like:
1. if Neymar played like a 2nd best player from January 2015 to January 2016
And if he played like shit after that
= is he the 2nd best player in the world or BOTH an awesome guy and a shitty guy, and when you sum it all, you get his "average" level
2. if Rakitic played awesome at a World cup and shit for Barca
Is he that guy from a World cup or a guy who struggles with simple passes?
Or somewhere in between?
3. if Suarez a guy who is the best No9 in the world or a guy who can't make a simple pass and he scored like 3-4 goals in a CL in the last 4 years?
Or he is BOTH?
The same with Arthur:
Is he that guy who offered like 10 world class matches in his 2 years at Barca?
Or is he a guy who struggles with simple passes like against Valencia or Leganes?
Or a guy who was subbed a half time often under Valverde because he was totally useless against parked buses at Camp Nou at 0:0 when we needed goals?
So, Arthur is 2 years have both shown:
1. a world class level
2. and a level not good enough for even wearing Barca's shirt (bad professionalism, tons of injuries, overweight, horrible stamina, slow, some horrible matches).
So, my point: why only looking at player's best matches (and going into extremes)?
I know, I am doing the same in a negative way (looking only at bad matches and bad moments), but I am doing it to some extent due to posts like yours, to "even things out" and to bring both sides of a coin.
So, if you want to rate Arthur and his "average" performance over the two years:
1. he struggled in the early weeks when he came
2. then he had good 2-3 Months from October 2018-January 2019
3. then he got injured and started to have stamina and motivation issues and he was pretty meh till the end of the season 2018/19
4. then he was very good at Copa America
5. then he missed the first part of 2019/20 season due to being tired from Copa America
6. then he returned to Barca and played 7 good matches where he was flying over a field
7. then his level started to drop in October of 2019
8. after that scandals emerged: Neymar, smoking, scooter, snowboarding, a fight with Messi, STDs
Since then he barely played, and whenever he played (except against Atletico 0:0), he was more or less overweight, with a heavy touch and horrible in general.
So, imo, it is not fair and measure Arthur with those rare moments when he is fit, motivated and when he plays well.
His overall Barca'a career during these 18-19 Months was quite meh.
To some extent, he is similar to Dembele: he played a few good matches, then he disappears or gets injured, and then he is not available for weeks and when he returns, he is rusty for a few weeks/months (remember his groin injury from last season when he was meh in March, April and May).
And when he returns to a form, he plays well only for a few matches and disappears due to random reasons again.
