Very often something like "6-12 months" is a good enough estimate. I've worked in software a long time and I really don't get why many people think it's impossible to give such an estimate. Most of us are developing glorified CRUD apps, it's not rocket science. And even rocket science can be estimated to a usable degree.
Really you have no idea if feature X is going to take 1 day or 1 year?
It's almost never fine, though. When it's fine, people aren't pressured into giving estimates.
> It likely is wrong, that's fine
The most you can do is say it. Communication demands effort from all involved parties, and way too many people in a position to demand estimates just refuse to put any effort into it.