UE4? The same UE4 that powers games like FFVII Remake, Days Gone and Returnal?
Well, with UE5 and the power of Lumen and Nanite they should be able to make a Super Mario World ripoff.
It just happens to be in UE4, which is a mostly-okay development system for making 2D projects in addition to the more familiar 3D projects. (UE4 is also a development system for making plain or even ugly games instead of groundbreaking or AAA games. It's just an engine. It can make great games, bad games, or just whatever games.) DSOG got a little over-anxious in singling out UE4 in their write-up (really, there's not much purpose to mentioning the engine used as even the developer is not using it as a key selling point, given that anybody who looks at it will, as you have, be mystified what UE4 is doing for this project,) but it's not a special thing the developer is doing here in using UE4 for 2D, it's just not done very often.
Many of the processes you'd go through to make a 3D world are applicable to a 2D game level; your objects, your context triggers, your routines, your AI pathing, your mathematics, your implemented physics, your plugins, your assigned sound effects, etc, it's all in the same general terminology no matter what you're building, and not even on a "lesser" scale when it's not full-3D (a 3D project could be quite streamlined or basic, while a 2D project could be massive and complex,) just kind of different ways of doing things. UE4 is also a cost-effective and familiar development system which deploys dependably to essentially every viable platform and has a modern development suite system for inter-office collaboration and is known by a good portion of professional developers on the market, so if your shop is familiar with UE4, you'd give at least a look at UE4 as one option out there for what you're considering building. As is, UE4's support for 2D is not richly backed, and few developers have chosen it over something like Unity (there's
The Siege and The Sandfox, also Octopath Traveler, but not a lot of professional 2D producers have chosen UE for their games,) but it's a viable choice if you know what you're doing and do your homework on its quirks, and it's not "overkill" to use an engine built for elite projects on something so simple as this game. It's just an engine.
In time, there will also be 2D projects made in UE5. Whether anything in the new engine update will make any difference to a 2D project remains to be seen (you might be able to do some fun stuff with Niagara, at least?), but just because UE5 will power the next AAAA blockbuster doesn't mean it's of no use to pump out a Zelda clone.
(This isn't really stock-level UE4 2D, but it kind of shows a bit of how a game would be built in it.)