Some disappoints about my H8-H

Hi, I've got my Minix for about 2 years and I remember that this device was sold as 4K and other good features.
I changed the firmware but I'm still using a Kitkat version and when I play some videos on YouTube I notice some slowing down, etc. and for sure is not a network connection.
Why do I encountering this issues?
Now 1Gb Ram is not enough anymore?

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