This. Although it varies from warband to warband.
Some openly employ tactics and are more accepting of corruption and usage of the warp. (The Night Lord's captain Krieg Acerbus 'the Axemaster' comes to mind)

Others use it as a weapon but do not give the gods any praise or worship. (lots of of Iron Warriors fall under this)

And then you have the fanatics that praise the powers that be and such.

But yeah, I agree with OP. It would be nice to see some reflection of those that are hardly tainted, but still fight the Imperium.

Most undivided legions are less enthusiastic about chaos worship across the board (with the honourable exception of the Word Bearers), and their views on mutations, daemons, farsight and other 'blessings' of the warp vary. The Night Lords and Iron Warriors are comparatively hardline, the Alpha Legion and Black Legion appear more enthusiastic about the visible benefits, even if not necessarily the worship.

"Chaos Forces Who Do Not Employ The Warp" are wretched fools fully deserving the eradication they inevitably receive.

The minor warbands tend to dislike the warp and chaos, simply being renegades. But the largest warband of night lords are lead by the daemon prince Krieg Acerbus who has his own daemon world in the eye of terror.

All chaos marines use and are afflicted by the warp. This is not the same as worshiping chaos. It is important to not think of any chaos faction as a whole. Even those that are said to not be split like the Iron Warriors are still organized into hundreds, if not thousands of different warbands that constantly split off, change, and remerge with one another. Individual marines can find worship in any god, regardless of their origins. That's why it's so important that the four legions being presented in game are the undivided legions, as it's easiest to find individuals focusing their worship to any of the four gods in them. You can add plague marines, noise marines, berserkers, and sorcerers without needing to limit them by legion.

Of course, there always will be some elements in warbands, who will deny Chaos (Like Talos and Co.) and they are always will be in minority. Anyway, Chaos can offer you some... really interesting stuff...so their falling to Chaos is a question of time.

Very much hope the Alpha Legion makes a showing, what could be more fun to play than a chaos marine who could be a traitor but could be loyal... or could THINK they are loyal but their entire sense of whats right and wrong has been warped to much over the years to know for sure.

Don't get me wrong I'd love to play as the death guard as my god of choice has always been nurgle, but if it was a choice of any the Alpha Legion would always come out on top, their lore is amazing the story could be very interesting and their whole thing is varied tactics to keep the enemy of gaurd so they can have a ton of options for classes.

Hydra Dominatus!