It doesn't matter either way, unless Spain has different laws for tax evasion ignorance is not and never has been a defense for not paying taxes. You may get advice from accountants and lawyers but when you put pen to paper you're the one responsible for what your signing. If Messi was wronged by his accountant then he could sue him separately, but the tax fraud itself is all on his shoulders and nobody else's in a legal sense. If Messi is too bloody lazy or incompetent to actually keep up with where his money is coming from and where it's going then he deserves everything he gets.
Luckily for him he can afford to pay the fines plus whatever money is owed, otherwise he would find himself behind bars.
Do you hate Messi that much to want to see him behind bars??
Nobody is saying Messi is not ultimately responsible for this (if proven true), of course he is responsible for the content of a legal document that he signs. People are simply saying he might not be aware of any schemes or errors on the part of his tax accountants, agents etc.
Have you ever had your tax done by a tax preparer, a professional? If you are not so well versed in tax regulations, laws and provisions, all the intracacies etc., you are going to basically trust your tax preparer's expertise that your tax return was done in the accurate and honest way. And you are going to sign it. If something goes wrong, yes of course you are responsible, but can people call you a cheat?
Lazy or incompetent??? Wow. I guess I am one of those lazy and incompetent people! You are so damn smart, you do your taxes, you don't hire any professionals to do anything. You are a much better person than lazy and incompetent people like Messi!