Bounty is not waste of time is just that a bounty normally take long periods of time before they will their users, If not every bounties project are legit all though that there some bounties project that is scams that are created them; but their not common the only thing that bounty need is that you have to participate on all of their activities: So that you can able to eligible on the day of payments; seriously bounty consuming a lot of times in terms of work on their activities and that’s not all newbie’s are able to participate in the bounty projects accept the one that much knowledge about the bounties.
Wait, when did a person need knowledge to participate in a bounty campaign? You surely need knowledge about what you are participating in such as video reviews, articles, etc. If you are participating in campaigns such as having to make retweets and tweets or maybe make posts on Facebook or Instagram, you don't need any knowledge for them but all you need is accounts that has enough followers that match the minimum amount of followers required by that campaign.
Your other point about bounties not being a waste of time because most of them are legit isn't valid. Just because a bounty or a project is legit doesn't mean you are not wasting your time by participating in their bounty campaign. It's all about the amount of tokens you are receiving and the value it has. If a project is legit but its token doesn't have a good value and you got just a small number of tokens, you did waste your time, technically.