Can I rely on the estimate execution plan to recommend indexes?
There's a limitation where it will not give you missing indexes when the query plan is trivial, perhaps that's what you are encountering.

Right click on the SELECT operator and select Properties. Check if the Optimization Level is TRIVIAL.



I use the estimated execution plan a great deal when performance troubleshooting. It's rare that I'll have the actual plan. Regarding missing indexes, I don't just add what the plan thinks is missing. I test the index, variations of it, etc.