... or, you know, you could just match them with eachother and some bots, so they don't realize anyone is onto them, don't ruin the experience for others, and still get to play what they've paid for(sorry if DoTA2 is f2p ... but even there, the best players will usually have spent some money).
Robot Warfare on mobile seems to do something like this(you'll find references to "AI Hell"/"bot hell" on reddit). Part of what players don't like about it is that you'll have maybe one, usually none, lower-ranked human player besides yourself on your team, and the opposing team is usually all bots or all noobs, so you either shoot fish in a barrel or invent challenges/handicaps for yourself.
When I would let my daughter play on my account while I built up hers so she would have a good "mech" or three(she still doesn't carry matches or get more than a few kills if any, but surviving to the end of a match with her dad on her team is a big deal for a 7yo), I would find my account stuck like so for a good while. Honestly prefer it to playing with the super-competitive "elite", who all use the same OP bot and play the same ways as eachother(I legit prefer the smaller/weaker/faster mechs ... ones where I often would be the first to run out of lives in a higher-teir game).
EDIT: removed the s at the end of bot. There's one bot specifically that the Pay2Win wannabe's spam.