Issues which block usage of the tool

I want to collect a list of issues that prevent Flow being able to be actually used for a code base.

This is mainly missing config options, or performance issues related to missing config options. This list is just for basic stuff. Other issues like community, tooling, etc. are things that can improve over time, but if Flow cannot be run on your codebase, then there is not choice but to move to TypeScript.

- doesn't support module aliases (there is a PR to fix) - #7185
- not able to ignore all node_modules without getting "cannot find module" errors, and being able to include node_modules packages that do have typings (ignore config precedence) - https://github.com/facebook/flow/issues/7431 #869
- adding node_modules to `[untyped] ` still makes the server look for them on startup which makes server start needlessly slow (which you have to deal with on every config change). I want to ignore all `node_modules`, but have `import 'foo/bar'` work. This is not possible.
- search upwards for flow-typed dirs - #5183
- errors in libs in flow-typed dir cannot be ignored by any config option - https://github.com/facebook/flow/issues/6256

Comment and I can update the list so we have a prioritized list of community issues that are preventing usage of the tool. As long as we can use it on our code bases in the first place, then we would be happy to wait for other issues to be fixed.

Maybe having a tag called "blocks community usage" would be good to label issues that fit this description.