Uninstalling a package shipping with the image, won't free any flash space, and there's a reason why there's no opkg - there's simply no flash space available.
You need to build your own firmware image, from scratch.
TL-WR841N v14 is a device with only 4 MB flash and 32 MB RAM.
Not really suitable for the current OpenWrt any more.
The OpenWrt actually has wpad-basic-xxx as the default for most devices, since year 2018. Including ramips/mt76x8
You are likely using somebody's tiny stripped-down build of an old OpenWrt version (likely currently unsupported), where the minimal core things have been tried to be scrammed into the tiny flash, and thus only the minimal wifi driver has been selected as it just fits it.