No Fire Particles When Stepping On Fire In Creative

I think this is working as intended.

In creative player cannot take environmental damage and this animation does not occur to start when he steps into the fire block, as it does in survival. I'm sure the main purpose this animation holds is to express the fact that player entity is taking fire damage (so the player could understand why the hell he takes damage all of a sudden).
This animation is also supposed to 'scare' the user by partially obscuring its FoV (and thus lowering the ability to predict the in-game situation around himself) but I think it is much less necessary and more of annoyance when player entity is invincible.

it's just unecessary information because you are invincible

Well, in versions like 1.7.10, when I step on fire, it still makes fire particles on my screen.

Actually, no in 1.7.10 it does not show the fire animation on your HUD when you are standing in fire.
As for the lava part that is a feature confirmed in MC-7572
We need a mod to mark this as invalid or working as intended

Yes it does, I've tried it myself...
Wait for the screenshot!

Ookokokk, I just saw that there aren't any fire particles on your screen. But once it worked... O_o

Seems intended.

This is intended. It's the exact opposite of MC-7572, that being fixed is this bug.

Whoops, misread MC-7572. Actually not the opposite. This behavior is still intended however.