I can't take it.

Actually Oliver in S1 only had the training we barely see in S1 & 2 most of his training is off-screen after that Oliver's skills as a fighter are cemented, everything else he goes through is filler bullshit that just happens to tie into the theme of his issues he will face exactly 5 years later.

He's shown learning rudimentary lessons such as he tortures 1 guy and becomes an expert at it, he is seen learning basic Japanese or Chinese from a child and he becomes fluent with a flawless accent, he learns about mystism and meets an ally he never see's again until 5 years later yet somehow this 1 time meeting has these two guys acting like old friends, and honestly how does a guy like Constantine have the same mobile number for 5 years so Oliver can contact him?

Oliver at this point yes is a well trained fighter but apart from keeping the skills Slade & Shado taught him honed Oliver learns no new techniques or styles after that, Laurel in S4 should have a far greater degree of education in the martial arts than Oliver did in S1 same with Thea based on them actually having spent 12-18 months training and under multiple teachers and disciplines, oh I forgot Oliver spent what 2 weeks training with Talia also but then Laurel spent a month training with Nyssa so isn't it kinda of a wash?

Also you only need to see the other crossover episode which is the case for all crossover events, watch them all because they are meant to be seen as one solid story, but Kendra's backstory is only hinted at in Flash until the crossover and neither Hawkman or Savage appear prior to it either.

Edit: Not arguing the fighting skill logic is not BS, it is Diggle now has spent 6 years training with Oliver who has supposedly grown leap and bounds as a fighter himself, but Diggle barely looks any more competent a fighter than he was in S1, but Oliver can in a month go from being a plaything for Ra's in their fight to being able to best him in the rematch with just 1 months training if it? it's all bloody nonsense.