2.5 ships with Symfony Cache adapters that where proposed to Symfony 4.x, since it was accepted several  improvements have been made.

Backporting the changes will:

• Reduce requirements, phpredis from 3.1.3 to any 3.x which will help on platform.sh and some dev environments, Redis from 3.2 to any 3.x version
• After backport will be a pure backported feature, so will to greater extent be forward compatible with Symfony 4 and 5 (same namespace and overall implementation), and will mean less maintenance for us
• And more, see PR.