Hello , i have a survival world that its in the 7th year since start. But my problem is that because of all the updates and who knows what else my game its becoming increasingly harder to play because of lag/fps drops.
I have a decent computer so that its not the problem.
I did a tone of settings but still got a very low fps.
The world age itself is probably an arbitrary factor. Rather, it's what's in the world that matters. Being that old means it's more than likely got things built up.
How are you trying to play? Vanilla? Modded? Shaders? Render distance? Resource packs? Are you in a built up area that may have a lot of entities like mobs, chests, or redstone, or farms, or other stuff that may impact performance?
"Very low FPS" is a broad term. Specifics are needed. Is this is a low FPS across the board? Momentary stutters? Or low FPS that are consistent to certain locations only?
Performance in Minecraft is a highly variable and more specific thing than most realize. It's more variable than most games I've ever played. The game CAN run on a laptop with a lower clock speed, old dual or quad core, 8 GB RAM, and integrated graphics. Simultaneously, it CAN bring the fastest CPU and GPU to their knees. it covers the whole range, literally.
If you're not playing with shaders or at a higher render distance though then the GPU is unlikely to be a major concern, and then it's likely just "Minecraft being Minecraft", and being hard on the CPU. Modern CPUs are multi-core, but something can be CPU limited even if just one thread is maxed out or stalled (which CAN even happen with that particular thread below 100% utilization). Old saying, but with Minecraft, it's almost always the CPU.
Follow Princess Garnet's advice and isolate the source of your lag. Generate some new chunks. Does that make it worse? Stay in new chunks only with no contact with developed areas. Does that help?
Version changing shouldn't have much impact on lag because a 'version' is just a voxel grid in the eyes of another 'version', the rules of the game follow only that of the new version.
I note one possibility - when updating a pre 1.18 world, the old chunks going down to 0 have to be filled in from -1 to -64. That generation would only cause a once-time strain, but I don't know how it works - aka if it still carves caves down there, and structures. Because no caves means more occupied blocks in the voxel grid, significantly more. And I don't know how it affects underground biomes, which will try to show up down there in the debug menu (F3).