I get the feeling that some of the people posting here could not be more than 22 yrs old.
Putting a couple of things into perspective about EV (my final judgment on his first season will come at the very end):
1) Bad (defensive) football
True to some extent. We are not enjoying something very beautiful on the pitch, especially for Barca standards. We are seeing a compact side that can win games by being pragmatic in that it wins them by utilizing Messi's quality and not needing to set the whole team to attack and destroy its defensive shape.
Most would want something better. I share this concern entirely.
But, let's look for a second, why this took place. Some memory refreshing is useful here:
i) EV took over a barren land from Lucho. A team that had no character and no tactical plan and philosophy on the pitch, a team that was based entirely on the individual brilliance of its ageing superstarts, predominantly the MSN.
At the same time, he happened to take over at the worst summer in the recent history of the club. Losing Neumar to PSG, and having Real Madrid enjoying a unreasonably huge success with back to back CLs and dominating in Europe.
ii) The building of this team took place entirely in the months of September - October - November. Like most top coaches do, teams are built in the preseason and at the begging of the season, not in February, in April or in May. The last months of the season performance-wise and energy-wise are important, but always it's the part when what has been learnt during the first months of the season is consolidated.
What really happened those crucial months at the begging? EV after having lost Neymar, didn't have Coutinio, lost Dembele to injury very early, and of course had an awful off-form Suarez that was conceding possession with every single touch. In other words, the had only Messi as attacking force to build the team on.
On the other fronts, he had an ageing md of raki-iniesta-busi who could not cover ground for their lifes.
All these taking into account, left him few options of what he could do with the available squad at his disposal in order to build something sustainable that can challenge for the title with some good chance.
And he came down to this 4-4-2, with defensive-oriented wingers in the non-Barca quality Gomez, Vidal, Deniz, Deulofeu, and fielding in Paulinho wherever there was a gap.
Many would argue that he could come up with something better. It might be the case, but we don't have any evidence for that. And of course, for people that want to play 4-3-3 no matter what, you have to consider if you would have liked better the possibility of an all-attacking 4-3-3 with messi on the right, iniesta and raki high up, full backs on the opponents half, and the team suffering defeats like that from Roma every other week, when playing any decent side on the counter. (Given that you have realized we don't have anymore the squad to play like in Pep's era)
I think it's clear that EV decided entirely based on what material he had at his disposal. Remember that he was practicing that hybrid 4-3-1-2 with messi as false 9 and dembele-suarez on the wings before dembele getting injured and realizing that suarez is atrocious there and then. We don't know what would have happened if things were different in terms of squad. And likewise we don't know what WILL happen in the future if EV has a preseason to reshuffle things, with Coutinho, Dembele from the start and with two more top-shelf players coming.
No coach changes things in February and March. So all the shouts about not integrating Coutinho and Dembele are not very profound to say. Coutinho and Dembele fell victim of being absent when the tactical strategy of this team was designed in the first place.
Given the above his domestic record is nothing sort of exceptional so far. That might change if the team collapses from now onwards. But winning domestic double with unbeaten record, with that mediocre squad we started the season with, i am not so blind to say it's not a success.
CL elimination was a disaster, which, nevertheless, even the greatest haters of EV could not see it coming. And they could not see it coming for a reason: The bad performance against Roma away had nothing to do with EV tactics. We didn't lose to Roma because we played bad football. We didn't play good football in the first game, bur we won 4-1. It is a problem that runs many years back as Busi said and has to to with mentality issues.
Just refresh your memory: we went out again in the QF, like in 2017,2016,2014. With the exception of 14/15, the last years we are not there consistently..
2) Rotations
Not good enough. And we paid the price in the fatigue of the regulars.
Is it a sign of cowardice though? Not necessarily. Look some miles northern to see how much Pep rotated this season. For 4 months the trio fernandinho-de bruine-silva was getting rests only in League Cup games (that means playing EPL, CL, FA cup). Of course Pep can do that more easily, cz Man City is much younger team. Is the age of our squad EV fault? I don't think so.
Point being: rotations cannot take place successfully most of the times. They destroy an already built chemistry between the regulars. That's why majority of coaches don't want to rotate much.
And this is maybe the only quality i appreciate in Zidane: he is maybe the first coach of a top-tier club that managed to rotate so excessively and bring in titles despite that.
Lack of timely rotations and bad football is something that's hard to look over.
Although, the latter, as you said, was also a byproduct of difficult circumstances in the squad.
Also true that mentality issues are largely down to players.
Going forward I have no doubt that we would be playing better next season with Coutinho available and Griezmann or someone else coming.
Remaining issue is stubbornness and fear that manifests in lack of rotations and general disregard for Barca future.
Can we find someone that is a visionare, loves Barca and is a great motivator?