Why not update ??😞😒😟

An iPhone 6 can't be updated beyond 12.5.5, it doesn't have the hardware needed to run anything higher.

If you need a higher iOS version, you will have to purchase a newer phone.

Your iPhone 6 Plus does not have the resources needed to run operating systems higher than iOS 12.5.5. Your phone has reached the end of the line as far as updates.

So, if you have apps that require a newer operating system, you will need a newer iPhone.