My jiu jitsu coach once said "if you're not playing, you're not moving."
I offer two ideas:
In her research paper "Playfulness: Definition, design, and measurement", Lynn Barnett from University of Illinois at Urbana-Champaign writes "rather than regarding play as what the child does, the better way is to focus on play as an internal predisposition to be playful." I'm not inclined to gatekeep playing games to children. I believe play has its role in any facet of life, particularly in research.
In my experience, spontaneity and humor seem to be the principle generators of novel ideas. Particularly, the engagement of play is encouraging and inspirational. We want to try out things to impress, and failure is acceptable because it's a game.
There will always be a place for order in moderation. However, rigidity is a fixation on structure that seems to directly compete with the play mechanism. This rejection to spontaneity opposes nature's proclivity to change. To circle back to jiu jitsu, when we are rigid in sparring, we are wrongfully assuming things are/will be like the way they were. This is a losing play.