I like either Looking for new servers or Get some new nice Texture pack
sometimes i even make my own Texture Packs

turn day night cycle off and leave it at night lol

Try datapacks. They're like mods except they're a part of the game, more vanilla and don't cause lag at all. You could also try making your own server using my tutorial on my PMC profile which could be a really fun to try out :P

Check out Mumbo Jumbo's video about fun things to do in Minecraft. That could give you some ideas!

Also, I feel like often Minecraft is a lot more fun when you have people to talk to, so servers are a really good option, or you could also consider live streaming your gameplay.

I would recommend you try and take part in different communities or servers :D
Other than that: In-game, you could try and make / recreate mini-games or games in general, using command blocks. I can tell you from experience, that recreating a simple game like Spleef using only command blocks, and then playing, what you've just coded, with some friends from a community is an amazing feeling :D

Other than that, you could always make guides for other people and then upload to your PMC :D

Hey, I heard mods make you lag. Don’t worry, I had a bad computer too! I would recommend getting mods for Minecraft 1.7.10. They seem to cause the least lag because they are relatively old and the Vanilla game has very few resources to load. I got about 30fps on a laptop with an integrated graphics card. As long as you keep the mod list to about thirty, you should be fine.

give yourself some weird and crazy ideas put them in a hat then build em in creative!,

for survival i would say do one or more of these:

1. Get mods
2. play with friends on LAN or realms
3. play on servers like hypixel with gamemodes like hungergames or skyblock

Hardcore is a fun mode to play. I only recently started playing it even though I've been playing the game for eight years lmao. Try and make some badass builds or art by gathering resources, dyes etc without dying else you lose it all :s

Try getting all advancements, when you do that, you could try with an advancement datapack.

I've been having this problem recently as well so I'm trying out new things with it such as playing online, which has helped a bit and also spending time playing modded helped as it meant when I came back to vanilla there were new updates. I would say however that you shouldn't try and force yourself to feel "it" again, you might just need a break from minecraft most people do after awhile.