Are you taking inflation into consideration when you compare ROI from Steem bots with ROI for other cryptos. Last year, we had about a 25% increase in supply of Steem. If the bot ROI for last year was less than 25%, then that is a very poor return.
The reduced supply of SBD should give us closer to the 8.5% for 2019. Maybe the ROI will look a little better. Selling votes through bots is not great a return. If you want a great return, invest in something that brings money from outside the Steem ecosystem. Delegating to a DApp and obtaining a share of ad revenue could be an example of a better return.