The main problem I saw about bots was that they were syphoning, for themselves, a good chunk of the total DEC rewards, while barely owning any cards but the 10$ Starter ones.
Also, they had an unfair advantage by knowing the cards of 99% of the players beforehand due that weird option we had 'on' by default until a few days ago.
But I honestly think that Splinterlands solved those 2 problems really fast: they removed from the game the whole thing about seeing the other player's card; and they also removed DEC rewards from players without in-game assets.
Now, bots are good for other players: they have to purchase and hold assets to be able to receive DEC (thus increasing the demand and the price of those assets for everyone else), and they also are easily beatable as they'll end up being way worse at the game than an actual person thinking. For good players, bots became a punchbag.