Welcome to business where resources are not infinite. One of Unity’s biggest downfalls is that it tries to be a jack of all trades. This has resulted in a half-***'d platform to develop on with the only saving grace being the Asset store’s ability to fill in the massive holes in the engine. In doing so, you end up with a fractured workflow, horribly engineered cash-grab add-ons, and reliance on 3rd party support.
But sure…you can develop on Mobile and any other platform on a potato laptop…until you have any project of meaningful size, at which point Unity becomes less performant and quite frankly dated when compared to the same thing in Unreal. GMS is arguably better for 2D and Unreal is the king of 3D…which naturally leaves Unity to mobile…which it won’t be able to compete in forever as Epic is a more profitable company (more to invest) and mobile technology is rapidly advancing.
To top it all off…Unity has an atrocious development cycle that leaves huge gaps and long-standing bugs between versions.