A lot of it depends on exactly what you are trying to achieve.
Landing Pages can be a lot of different things these days. Originally a landing page was a page optimized for human engagement and ‘stickiness’ given a specific known interest, but not necessarily a page you expected to rank well on search engines. Instead we used to sometimes generate doorway pages to deliver specific search users to the corresponding landing page, or we’d have dedicated landing pages for specific ad campaigns according to the demographic where that ad would be placed, etc. The point of a landing page though was always to be engaging for humans, to connect and appeal quickly to whatever specific interests or whatever we knew about them, and to present the best possible first impression to a given subset of our customers or users.
In the years since, people generally picked up the idea that ‘doorway pages’ were bad, so stopped using that term, but used ‘landing pages’ to mean exactly what doorway pages were. The focus was all about ranking. The fact that you made your primary (point 1) a comparison to what was ranking from other sites leads me to believe that you learned mostly this latter meaning of ‘Landing Page’.
With all of that in mind, I’ll assume from here that you mean to create a page that can rank well on search engines for the given keywords, but will also (point 2) provide a decent enough user experience that they don’t immediately bounce.
Understand however that you are using search terms that have a naturally high bounce rate because of the type of search they represent. When someone searches for “iphone 12 cases” they are shopping around, looking to see lots and lots of options and alternatives, and will pretty much always want to visit at least a half dozen sites with a broad range, more sites if the range at each is less broad than expected.
For search terms relating to products such as phone cases, or for screen protectors, the size and weight of the phone, and the case, have absolute direct bearing and relevancy. The size and weight of a phone are key factors in where you expect to hold it (wether it is a comfortable pocket size, or something someone would keep in a bag or purse, for example) how hard it might bang against things (including if dropped) and even on how likely it is to slip from a hand more or less than typical. Mentioning those kinds of things on a landing page can help engage visitors, showing that your page really thinks about these things, and helps them to do so too. Most especially, giving them something memorably different about your page experience helps your page and site ‘stand out’ from the competition, and if many of the companies have a lot of similar cases, makes it a little more likely than otherwise they’d select and come back to yours.
Being the same as everyone else’s pages is not good SEO. Being the memorable, different, and preferred one is where the money is at. Making your cases, or at least, your way of presenting and selling them a preference, and not ‘generic’ can be critical to maximising value, AND to getting more links, so you rank better too.
Personally, I wouldn’t have AI write my pages at all. That’s partly because I’m a very experienced writer and can turn out a post like this straight from my mind without any real effort, and I find it harder to adapt the writing of another (including an AI writer) than to just go with the flow and direction of my own thoughts.
It is partly because SEO is a big part of my skillset, and what I’m both known for and paid to do, and you never outsource your primary skill to a lesser worker (unless you want your employer to think the same way). Sure, it is effort and work to do it oneself rather than at the click of a button, but it is work I’m paid to do, whereas clicking buttons is something the client would rather do themselves.
Focus your page content first and foremost on making people (1) stick with the page and look around deeper than they might otherwise, (2) be impressed enough to remember your site and have it stick in mind as they visit others, and (3) be the one different enough to be the one people link to. Rankings come easily (and more naturally) once you nail those 3 parts.