Islet Online is a sandbox-style MMORPG. It's an indie game developed and published by Morenori Soft in 2019. It is all about digging and placing bricks to build your own land. And with various materials from wildlife, bricks can be combined to make useful items, too. Whenever you act, your character gets experience.
The game is very lightweight to run; all new laptops can play Islet Online.
The RAM requirement of 4gb is easily met, though 2gb is enough to meet the minimum requirements.
Also, note that at least 1gb of hard drive space is required.