So what exactly is the problem? I see a lot of talk about dependency hell and node_modules bloat but I don't really hear much about what the actual downside is

So what exactly is the problem? I see a lot of talk about dependency hell and node_modules bloat but I don't really hear much about what the actual downside is. Is it performance (I haven't experienced it)? Is it taking up disk space (I have terabytes to spare)? Does it add complexity (I would argue it reduces complexity)? What exactly is the problem?