This is a well known issue... The starter needs replacing.

The starter needs nearly 100% of the cranking amps when new to turn the engine over... as time goes by this increases due to dry joints etc.
Eventually leading to the click and no start.

To clean up the starter it is a significant amount of work and by the time you have invested at getting to it the replacement part is a minor addition. Cleaning up only lasts for a while and you are back to square 1 anyhow.