The title of this post is hyperbole of course. Beaufort wind scale is an excellent tool for estimating wind velocity .
I sailed on several smaller vessels, tugs, the Aleutian freighter etc that were not equipped with anemometers and I can't recall ever thinking we needed one.
Sailing large vessels deep-sea is another ball game however. It's less seat-of-the-pants than smaller vessels. In the case of wind velocity, ideally both observation and measurement methods should be used and the results compared for miss-match.
Same goes for tracking tropical cyclones, it's not prudent replying on a single source of information.
Another example is speed. On the small vessels it was simple, we knew from our rpm, observation and loran (pre-GPS) what our speed was. Now we use rpm, the slip table, Doppler for ground/water speed. We look at vector components , we make comparsions between SOG, SOA and modeled speed from wx route programs. We analyze the various factors, current, wind, sea, swell. We get very good at estimating speed in various condition but we used various tools as an aid.
It's all about understanding what is being measured. An anemometer measures wind velocity at it's location. That's can be useful information if you understand it's limitations and know how to use it properly.