Diablo 4 is omitting a staple quality-of-life feature from past titles - the tab overlay map. If you're new to the series and don't know what that is, essentially, pressing tab opens a layout of the area you're in, but it appears on top of the screen rather than in a separate pause menu. Diablo 3 moved it to the top-right to try and make it less intrusive, almost appearing like a larger and more detailed minimap, but Diablo 4 is getting rid of it altogether.
As reported by PushSquare, its absence was confirmed by Diablo lead Rod Fergusson on Twitter in response to a fan asking, "Will there be a TAB overlay map eventually added to the game?" Fergusson said, "No plans at the moment."
For the time being, you'll have to stick with the minimap and waypoint markers to navigate the Mortal Realm. It looks like that'll be the case even post-launch, though many on the subreddit say the minimap is a more immersive alternative that they're happy to use in place of the overlay, while others say it could still do with some tweaks, like an option to zoom out, a square variant, or settings for enlarging it.
The news hit the subreddit and quickly saw a thread shut down by moderators "Due to the mass amount of uncivil comments going on". Players are split down the middle, with many celebrating the news while others say it's another notch on Diablo 4's Bladebuckle Plated belt, inevitably leading to chains and chains of arguments in the comments.
"I also think the overlay map in [Diablo 2 and 3] [is] intrusive," BoilingCoconut commented. "We are so used to the old way of seeing map, it's a habit. But I do like the D4 approach. The ability to place a marker and guide the player to where they want to go is much better and less visual noise."
WobblySlug had a different perspective, "Overlay is a staple in every ARPG I've played, really strange choice to not include it (or have plans for it). Minimap isn't the same, I like to be able to quickly toggle the overlay - take in the information - and then toggle off."
However, between the 'good riddance' comments and the 'how dare they?' lot, there's an in-between, with some confusion as to why it isn't simply an option so that those who want it can use it, and those who don't can ignore it. Others say the same of the minimap, asking Blizzard to implement an option to turn it off.
Maybe we'll get more UI customisation down the line, but on launch, you'll have to get used to a lack of an overlay map.