How many different (martial) arts should you explore? Pick one and practice it over your lifetime to become the expert of experts? Switch frequently and try as many as you can to have the broadest possible perspective? I think the answer lies somewhere in the middle.
If you only ever study one art, chances are you will not fully understand it. If you get distracted by trying to do too many, then most likely you will not get anywhere with either one.
Avoid tunnel vision
While I strongly believe that you need to spend a lot of time on one art to really understand it, and maybe eventually even master it to some degree, it also limits your perspective to a problem and its solution to only one single angle.
I often noticed, that I would understand things on a deeper level, when they were presented to me from different angles. Sometimes the Karate explanation made more sense to me, sometimes it was the Tai Chi approach and sometimes I would finally understand a difficult principle while trying to practice an Aikido move or Jodo strike.
Don’t miss the tree for the forest
On the flip side you need deep and enduring exposure to a certain framework of thinking or philosophy, to understand it on a natural level, to feel it. To “make it yours” (Morihei Ueshiba).
So if you try to learn too many different things at the same time, it will distract you more than it will help. It’s hard to combine teachings from external arts like Karate with internal systems like Tai Chi if you didn’t get to the level of seeing the principles yet. It will all just seem like a big mess of disconnected contradictions.
Know your core and expand from there
Start by picking one martial art. Practice it. Practice some more. Keep practicing until you reach a level where the underlying principles start revealing themselves and until you don’t have to ‘think’ about the movements anymore.
Then go and add small doses of other styles and arts to it. Observe what that teaches you. See what new angles and perspectives open up for problems that you already worked on (and maybe struggled with). Be open to understand moves that you have already practiced from a new and different angle. Don’t rip and replace, rather add to your knowledge.
You might shift your primary art over time as your interests change, but always have a primary art that you go deep on and see others as supplements.
If you experiment with other arts, I would recommend to seek significantly different perspectives. If you do Shotokan Karate, don’t do Wado Ryu. It will teach you a master’s preferences, but only few new insights. Add something different like Aikido or Tai Chi. If your focus is an external martial art (like Karate, Kung fu, Tae Kwon do, etc) then add an internal art (like Aikido, Tai Chi, etc) and vice versa.
Dip your toes into something new. Try it out long enough to get a good sense for the ideas and principles underneath, but know your home base. Know your core and expand from there.