Attending an event depends on your career path or interest in that field. How useful the event will be depends on your intention for attending. If you want to start a career in the blockchain sector, then it is worth attending. Attending blockchain seminars might be also beneficial to people from different fields so it might not be a waste because your career can be integrated into the blockchain system.

But it is also important to consider the content of the event and how proficient the organizers are. Most of these events are just organized solely for profit-making without any genuine intention of imparting knowledge. I have also witnessed these seminars where the organizers will introduce an investment scheme or a worthless altcoin for participants to join or buy. But if you are sure of the organizer it will be good to attend. You have to also consider the cost of the event, if you can afford it or not. There are diverse quality videos and materials you could have access to that can give you standard lectures on the blockchain.