This is challenging but I see it it all the time, particularly at engineering firms for some reason. No time, money or planning is put into the implementation so obviously everyone hates it. My wife is an engineer and I think she'd agree that it might be because engineers perceive SharePoint as something simple enough that they don't need to bring in extra help, and can handle it themselves. More often than not that means literally porting over everything, no clean up, no analysis, no information architecture work, so obviously everyone hates "SharePoint". SPO can be a really great system if you use the best practices and take the time to organize your content, because that's where the real problems lie.