What's actually breaking your automation projects

I've been tinkering with automations for a couple years now and honestly the biggest headache isn't the tools themselves, it's everything else. Legacy systems that don't play nice with APIs, processes that shouldn't be automated in the first place, and. then there's the fun part where someone changes how they do things manually and the whole workflow breaks. Plus you've got people freaking out about job security which is fair enough. I've seen projects fail because nobody actually owned them afterwards, so they just rotted. Curious what's hit you hardest. Is it more the technical side like integrations being a nightmare, or the people/process stuff? And do you find it's worth automating everything that CAN be automated or are there workflows where it just creates more problems?