As mentioned from various answers above, there is not right or wrong here. It depends on what you want to achieve, what you want to become.
The testing industry has advanced a lot in the last decade and various roles have appeared, test analysts, manual testers, automation testers, etc.
I am old fashioned and believe that balance is the key to achieve anything. If you want to become just a coding machine that does not "care" about the context behind what you are writing about, then no, you do not need to know how to manual test.
But to do a good job, you will need to be supported by an appropriate team structure. You will need to have specific and very detailed test instructions provided to you, so that you do not need to make assumptions or lose time asking questions. Does this team structure exist in many companies? Or many are asking for "automation engineers" and require also test analysis parts?
Context is important and testing automation is not the solution to all our problems. It is a tool and should be used as a tool.
When a new product release arrives, you should have a good automation suite built up to cover your regression testing and manually test the new features. During manual testing, you also build your test cases which will be eventually used to enhance your regression suite by automating a part of them or all.
So, if you want to reach a state where you are a complete engineer and not a tester or a coder, you will need to work on all the potential paths initially and achieve fundamental knowledge on all available aspects. You will need to know the basics of exploratory testing, know how to write a test case, how to report a defect, understand the context of the work product at hand and how it needs to be tested and then, this knowledge will guide you to automate your scenarios. You would know the risks, know the pitfalls and work on those when automating, focus on what is important and not lose the big picture.