I think everyone goes through this at some point, feeling uninspired, or needing something different. It also sounds like you've already identified a possible solution in your post, by switching to a simple setup. I think if you know that a 50mm lens feels the best to you, you should just throw it on a camera and then use nothing else for the next 2-4 weeks. Fall back in love with the gear you are using and it will translate in your images.
For others who might find themselves in this situation at some point (which face it, is likely to be any one of us at a given time), I like to think of simple challenges, most of which usually involve working within a set of limitations of some sort. This is actually what Ken is proposing to himself, he's just already decided to choose his parameters based on his own personal history.
1. The one lens challenge
Ken's parameters fall into the "one lens" category; choose a lens and use nothing but that lens for a specified period of time, typically at least two weeks, but often as long as a month. This is a great way to get to know new gear--use it for everything. It's also a great challenge if you happen to have a some gear that goes unused for a period of time. I rarely use my 14-28, and it's not really a practical every day lens. But the few times I've forced myself to use it as a walk around lens I've gotten some really great images that have become favorites.
2. The one subject challenge
Similar to the one lens challenge, choose one subject and shoot nothing but it for the next 2-4 weeks. You can vary the actual object in your frame; for instance, maybe you choose to focus on chairs - you don't have to shoot only one chair the entire time, you can use chairs from all over. When we force ourselves to look at or for only one subject, we have to really get creative in how we frame, light, present that subject so that everything doesn't look like a rehash of the image before (I personally am falling into that category with my summer flowers - most of them look like each other, but they are stuck in the ground and I am trying to evade mosquitos). But this is also a good way to force yourself to look for your intended subject off the beaten path; I often love my images when I find a flower that is one my walk, vs one in my yard, because it gives me a different background or color or shape.
Last fall I was bemoaning to some friends in a group chat that I was feeling uninspired, and one of them suggested a light study to me. I initially discarded that idea but then came back to it, and working through that has me now looking at light very differently every day, whether I have a camera in my hand or not. And also while not every (or even most) of my current images have more dynamic light than they used to, when I find that the light is amazing, I'm more able to harness it than I was before I took on that challenge.
You can also use this challenge for something like shooting only one color (look for blue, red, purple, etc) subjects, finding scenes only in your house (limit even to one room), finding scenes only with a dog in it, only including doors....whatever you one, just find a single subject to repeat over and over again and see how differently you can present it across a body of work.
3. The day in the life challenge
I've never personally attempted this challenge, but a lot of people have sucess in taking one photo every hour throughout the day. It forces you to look at the mundane and make it interesting, and it also gives you a great way of capturing your average life to look back on in a year or five or ten and spark memories of what life is like now. As I said, I've never done this specific challenge, but I do have a random assortment of images over the years from my kitchen window, and in the eleven years that we've lived here, it's amazing how much the view through that window has changed. If you asked me, I'd say only one or two things have changed, but it's been a lot more than that, and I could lay out a chronology of changes if I had to.
4. One subject over time
This is a longer term project, but I follow a group of people on Instagram who determine a location at the beginning of the year and then use it once a month to document something. It's a fun way to track seasons and growth over the course of a year. Some people choose a spot in their house or yard, and others choose some where more scenic and use it over the year. Most of the people I follow are documenting their kids along with it, but you can just choose a lake or a water tower if you want.
5. A 365 project
I personally usually find the best way to get out of (or avoid) a rut is to just shoot every day. Make it a mindful practice where you *have* to pick up your camera to document something. Not every day will be a masterpiece, and some days you will hate your camera. But other, rarer, days you'll find the most magical thing to shoot, and it will all be worth it. I don't shoot every single day any more, but I did complete a 365 in 2018. I don't think it propelled me to the growth that some people experience during the project, but it did really engrain a sort of mindfulness in me that I still have when using a camera. It's rare that I don't shoot something in a single day now, but I give myself some grace to take a day off here or there now, but it never lasts more than about two days because I just miss holding a camera and looking for something new.
