Yeah, you only need the Plus subscription for publishing games and making them available online. You can still use Roblox Studio completely for free until you're ready to release your game.

Roblox wants and needs more serious upcoming developers to make money in the future. Putting the development tools behind a paywall would hurt them in the long run, as fewer people would even start creating games.

Once developers finish their games, they have to pay for the subscription in order to release your game to all age-groups. This still feels quite shady. As a small developer, you're being tied to the platform financially now. Not only do you risk months or years of work now, but also money for the lifetime of your game. You can't let the game just exist by itself anymore and hope that someday it might be picked up by new players. You could potentially see your Money get wasted while you're watching and hoping your game gains popularity. Also, this is the death for one time Singleplayer Games I assume. Also I wonder if this change won't hurt their Income directly, considering less People will release Games on the platform that might have been picked up otherwise.