There's no built-in weather. However, there are mods which add this feature and extend it far beyond what you might expect from basic weather.

Yet mobs can be installed through mods or subgames, but they are laggy because of bad lua performance.

New players might be off-put by the extremely simple base game. Compared to games like Minecraft, very little is provided out of the box; instead the base game is intended to be built upon by adding mods.

Minetest is obviously an opensource implementation of Minecraft but the only problem is all the mods made for Minecraft do not work in Minetest. They could have designed their clone in such a way say fix it at 1.7.10 forge so that you could load up forge mods straight up and have them work somewhat. There's so much great content for Minecraft that is completely lost and unusable in Minetest, however at this pace of developement, maybe that will change in the future.

Parts of the games's graphics and functionality are really bad. Mob mods or default mobs look like a 4 year old drew them. However, the devs seem to be slowly sweeping through these issues. Come back soon if you don't like what you see yet.