I think it's a great idea to explore the possibility of using a bot to earn income from your Splinterlands cards. The rental market is definitely drying up, and the value of your cards has decreased. However, if you can find a bot that can consistently earn you more than the rental market, then it could be a great way to increase your income.
I've heard good things about Xbot.App, so I think it's a good place to start. The free trial is a great way to see how well it works, and if you're happy with the results, you can always upgrade to a paid plan.