Exactly, poker is a zero sum game, if we want to earn money then someone else at our table needs to lose money, if everyone is a good player and we have a similar level of skill then over the long term the players are just bouncing money around and no one earns anything except for the house with their rake, this means that new players or players with low skill are needed but if their number is low then sooner or later they will give up and you will be back at having the problem of only playing against skilled players, so what is needed is for poker with cryptocurrencies to become way more popular so the influx of new players is constant.
You are talking about players that playing for money. For some of them playing poker is a work. But there are lot of players, that playing for fun. They brings some money just to lose it. It is not a problem for them, they pay for getting fun. And they are playing just occasionally. They giving money for rake and pro players.
Not entirely, more broadly I am talking about skill levels, even if you do not consider yourself a professional and you are fine with losing some money at the casino it is completely natural to still want to win, and if your level is high enough so it matches the rest of the people on the table over the long term you will lose money due to the rake and not the skill of the other players, this scenario happens regardless of whether you are a professional or not and it is entirely dependent on the skill level you happen to have.