How to debug Sitecore Helix Feature using Visual Studio 2017?

Agree with Richard's Answer. Just keep few points in notice while debugging:

1. Attach you process to correct managed pool

2. Publish your dll's to your instance so that your breakpoints should load properly. Keep your profile in "Debug" mode and not in "Release"

3. Your feature and foundation must be published properly to your instance.
4. Your controller rendering has correct details of your controller and action method and dll.

Its perfectly possible. You just need to attach Visual Studio to your w3wp.exe process.

1. In Visual Studio, select Debug / Attach to Process (or press CTRL+ALT+P).
2. In the Attach to Process dialog box, find the program that you want to attach to from the Available Processes list. For this it will be one of the w3wp.exe processes:

You will need to select the Show processes from all users check box.

3. In the Attach to box, click Select.

In the Select Code Type dialog box, click Debug these code types and select the types to debug.

Click OK.

Click Attach.

Ref: https://msdn.microsoft.com/en-us/library/3s68z0b3.aspx