The reason complaints about the GDPR are made to Ireland is not that simple. It’s because as part of the actual GDPR law they selected one government agency to be responsible for enforcement - and Ireland’s privacy agency was the one selected. It seems it’s not uncommon in the EU to do this. It does not prevent nationsl governments from enforcing the GDPR but it does mean general complaints and proactive enforcement are Ireland’s responsibility.
Obviously, knowing how cosy Ireland is with the tech giants, one should wonder if it’s a coincidence. It seems that Ireland’s support for the GDPR was negotiated with this condition - that their understaffed, underfunded privacy regulator would be responsible for enforcement. I am convinced tech company lobbyists pushed for this also, knowing what would happen - that essentially no enforcement would take place from them.
So essentially the GDPR is great on paper, but with Ireland being responsible for its enforcement it is essentially toothless.