You say your foot slips out. Why ? Because you pull back and the strap isn't tight enough to hold your foot? Does the strap stretch? Or slip in the buckle? Break? Do you tighten the strap after getting rolling and putting your foot in? What shoes do you wear?
A lot of questions because until we know more, we have to either guess what is happening or spout generalities. I've been using toeclips and straps for half a century with little issue but: I ride with quality toestraps pulled tight (and I treat that leather with Snowseal dressing) and wear cleats that fit over the pedal cage. Even if I"m wearing street shoes, I pull the straps tight. And yes, I still fall over when I forget to loosen the straps. I also ride at times in conditions where pulling a foot out would be a life-changing injury. Whereas the "oops! I forgot to loosen" always happens at a standstill.