Deleting an app or two, clearing a bit of cache, and the "storage full" warning disappears for a week before coming right back. This cycle is familiar to almost everyone, and it usually persists because the actual biggest storage consumer never gets addressed — it just gets nibbled around the edges.
Apps, even a lot of them, rarely account for the bulk of phone storage on a device that's been used for a while. Photos and videos — especially videos, and especially anything recorded in high resolution — are usually the single largest category by far, often dwarfing every app combined.
Every photo, video, and voice note sent or received in WhatsApp groups gets saved to your phone's storage automatically by default, which means active group chats can quietly accumulate a large amount of storage over months without anyone deliberately choosing to save any of it.
Most everyday apps are a few hundred megabytes at most — deleting several barely dents a storage problem that's actually measured in gigabytes of accumulated photos and video. This is why the "delete some apps" fix feels temporary; it's addressing a small fraction of the actual problem.
Going through your camera roll and compressing the photos and videos you want to keep — rather than deleting memories you don't want to lose — can free up a genuinely large amount of space without sacrificing anything you actually care about, since much of that storage is redundant image data compression removes.
A single big cleanup session helps temporarily, but the storage fills back up at the same rate unless the underlying habit changes. Periodically compressing recent photos and videos, and being a bit more deliberate about what WhatsApp media actually needs to stay saved, keeps the problem from fully returning.
If "storage full" keeps coming back no matter how many apps you delete, it's worth checking your camera roll and WhatsApp media specifically — that's almost always where the real space is going.