Main differences - in 2018 even scam project bounties distribute rewards and got listed. Now transactions and listing became expensive, and it makes people think that the amount of scam has increased. If you have participated in bounties in 2018, then go ahead and check projects, that have distributed you rewards. You would find that they most likely are already delisted, and have stopped developing or following roadmap long time ago.
Each period we see the market change, and of course, the mistakes of the past cannot continue to be repeated. Everyone has a lot of skills to moderate the project, and currently the shitcoins that appear are very easy to check and report, so even though there are many bounty programs, they are almost always scams. But as far as I can see, there are still many opportunities to earn bounty money if we work hard.