I have never found going to seminars particularly useful for learning anything.
Most of the numerous talks are forgettable. For the few good ones, you can just use youtube as they are almost always uploaded these days.
The talk format itself necessarily means that you can never get too deep. So at best you have a summary. Many of the better talks are authors talking based on their book. So you might as well read the review and/or read the books. Travel also significantly affect your mental ability as you will likely get sub-optimal sleep.
Networking is of course, useful.
Corporations seem to recognise going to seminars and, more importantly, talking at seminars as indicators of ‘progress’. Are seminars, in some way, career-point farms? Many speakers are representing their company. So they are there to give their company presence rather than having anything interesting to say.
Personally I have found the best way to learn is to get good resources (a nice book) and then go through it and/or experiment yourself on training projects.
What have been your approach to conferences and learning in general?