They have every right to use the FOSS clients if they don’t want ads and don’t want to pay anything. Thing is there’s no reason to complain about a paid client existing. It doesn’t take away choice, it adds choice. FOSS devs will want to implement features they see in paid clients and raise the bar for paid client to add more features and then repeat. That’s a great thing for users. All this choice will lead to better and better clients, both FOSS and paid. What’s important is that lemmy is an open platform meaning we will always have choice. More choices are a good thing.