The sentence "I really enjoy it" is correct and usable in written English. You can use it in multiple contexts to express pleasure or satisfaction, for example: "I just ate some of my grandmother's famous cookies - I really enjoy it.".
I really enjoy it.
And I really enjoy it.
But I really enjoy it.
I cook and bake often — I really enjoy it.
But he added: "I really enjoy it, I love Chelsea.
"When I go there I really enjoy it.
I really enjoy it, it's a really pretty place.
I love the desktop app, it’s always running on my Mac. Ludwig is the best English buddy, it answers my 100 queries per day and stays cool.
Cristina Valenza
Retail Lead Linguist @ Apple Inc.