Given that significant advantages in a specific hardware leave out a lot of people that don't posses that specific hardware and leads to mining centralization, is there an active effort to improve the mining algorithm used in Monero to avoid this and harvest the computational power from many devices?
Based on above comments ... No. CryptoNight is the exact opposite of what "hardware-agnostic" means. In particular, CryptoNight is designed to run best on CPUs, and run less efficiently on GPUs and other accelerated compute devices.
An algorithm that is truly hardware-agnostic would run efficiently on any compute device.