You can support a club and not agree with their decisions.
supporting a club is love/hate but fans are unable to really force a change other than stop paying for tickets and leave stadium empty to get a charge for action to change
Again, different things. Fans cannot make changes as the management can but as I said a little self awareness wouldn't hurt and lightening it a little bit on the insults wouldn't hurt.
Most people wanted Ronaldo even though everyone knew what kind of financial effort that would take (me included). Before that most people wanted Higuain, most people celebrated the Arthur-Pjanić swap, most people liked the Marotta firing because a 'more modern' director was taking over (especially after a rumor broke out that Beppe was against signing CR), most people wanted Allegri fired the first time and even though most were hoping for Pep back then a lot of people quickly pivoted to approving Sarri, most wanted a complete rookie in Pirlo last season, most wanted Costa and Berna back then, most wanted Matuidi and Khedira gone at all cost and liked Rabiot and Ramsey because they were 'free' etc.
So if you were at the time 'oh yeah this is great' and now 'only and idiot would make those moves' then it's just revisionist history. Blaming them for not realizing their mistakes and fixing them sooner is a valid criticism.