Apple's default photo editor leaves a lot to be desired, it's simplistic and limited in capability.
My photo editor of choice and default option for as long as I can remember has been Snapseed. It is a comprehensive tool, includes all the standard photo editing tools and the user interface for which is apt for use on a phone. It also has more flexible tools such as curves, perspective, selective and brush edit capability, healing and HDR. It has an assortment of filters, B&W effects, film effects, grain, grunge, text and frames. It was bought by Google a while a go and it is completely free with no advertisements. It's a very comprehensive tool and for most photo editing purposes, is the default tool and the only tool.
Recently I tried out a different app and now use it as my default tool, Afterlight. The reason that I tried it out in the first place was, I wanted a tool that can do selective colour and hue adjustments and one that would support split toning. Afterlight, does everything that Snapseed is capable of, with the added colour manipulations. It also has a wider and broader range of filters. If you do require selective colour handling and split toning capability, then this is the tool I would fully recommend. It is a subscription model (circa £18 per year).
I did try out Lightroom mobile on an iPhone. I found the interface and userbility to be clunky and not cohesive. This is a purely personal preference/perspective.