I haven't blamed him for anything, just stating a fact that Dortmund are a worse team now than when he joined and they are, the point being that Dortmunds main problem is conceding loads of goals very easily and we have the same problem.
Its not embarrassing to state my opinion, we didn't need Zlatan, we needed to stop conceding silly goals, and we have the same problem now. Haaland won't fix that, he might help us score more but if we were defensively solid then we don't lose 3 - 0 to Juve and Roma or 4 - 0 to Liverpool. Look at the difference a solid defence has done for City or Chelsea recently, or Liverpool before that. That would be my priority if we had money to spend this summer. But I would still be excited to get Haaland too but I don't think it will make much difference if we keep conceding goals relatively easily.
In La Liga, you don't build a team to concede less but to score more.
If you play against Getafe, your goal No1 isn't to buy 4 good defenders but to outscore Getafe.
Playing in La Liga is a competition of 2-4 stronger matches, 4-6 average matches and 30-ish matches against very weak teams where your only goal is to score.
CL is a different story.
In La liga, the champion is a team who is more consistent in beating weak teams.
In a CL KO matches, you don't play against minows but against equals and this is why defense suddenly matters and why some attacking patterns from La Liga don't work in a CL.
About your EPL example, since they have more big teams than La Liga (City, Utd, Liverpool, Chelsea, Arsenal, Tottenham vs Barca, Real, Atletico) and more average teams, you could say that improving defense will matter more to City/Liverpool than to Barca, regarding league competition.
Regarding defense in La liga, I will give you a better example:
What mattered more in La Liga over years:
1) having Messi/Cr7 in attack and having an attacking team with bad to average defense (Barca and Real)
2) or having a strong defense and a defensive minded team without such power in attack (Atletico)
In La Liga, Barca and Real with strong attack are absolute winners over Atletico.
In a CL, the story is different and Barca's attack without defending is way more mortal in a CL matches while Atletico is not that sterile in a CL KO matches compared to La Liga matches (over the last 10 years).
So, there is a reason why Barca is historically buying 30m attackers like Ronnie and Etoo and 4m defenders like Marquez and Edmilson.
Or 100m Neymar, Dembele, Cou, Griezz and 30m Umtiti and Lenglet.
Against weaker teams, technique, domination and attacking win titles.
Not defending.
You do need some defending, but even for me, who is a fan of workhorses, for La Liga, it is always better to play 2 Pedris and 1 Rakitic than 1 Pedri and 2 Rakitics in midfield.