I don't know maybe there's nothing to improved in the wallet niche? For example, Electrum is a good solid SPV already and I doubt that it can be topple by any new or even old wallet in the market.
That depends on the type of software. I agree with you that the desktop version of Electrum is a pretty neat piece of software. It could benefit from a DEX, for example. Maybe even a non-KYC fiat on/off ramp.
However, the mobile version of Electrum isn't my go-to client for a mobile wallet. It lacks several functionalities of the desktop client and it doesn't feel right. It looks like a weekend experiment developed by some students 20 years ago because they wanted to see how difficult app development is.