You may not have given it much thought, but there's one subtle difference between classic First Person Shooters of the MS-DOS era and modern titles, and that's the position of the gun. Most modern games position your weapon to the right, which is arguably much more realistic if a weapon is in your right hand, but back in my day, guns were always in the center of the screen.
The good news is if, like me, you're a fan of the central weapon position, Doom Eternal has you covered, as it will feature a centered weapons view for that nostalgic kick. The idea behind a centered weapon was that it helped you aim more accurately, as crosshairs or even vertical camera movement were either not yet invented or a relatively new concept in the genre.
By lining the weapon in the centre of the screen, it gives you a much better idea as to where you're aiming. It's a staple of old FPS games such as Doom, Quake and Duke Nukem 3D. It wasn't a long-lived thing, as more modern FPS games eventually moved to the status-quo we are used to today, but given how iconic some of these early shooters were, it still has fond memories for me.
Arguably it's less realistic, but given nothing about Doom is "realistic", I prefer to just go all-in and revel in the fantasy and retro aesthetic of a centred weapon, so I am really happy to see this feature.