some what true.

technology stalled for a long time after fire and basic iron working because we were busying getting kingdoms and empires up.

many things were developed besides what modern people deem as technology. things like writing, culture, gods and demons were all in the experimentation stage for about 3000++ thousand years since the earliest recorded civilization

then we got to around 1000BC where countries more or less became stable in the more fertile plains and people started started to have fun with science.

mathematic,medicine, printing and stuff that were considered the basic needs of living prospered during this era for about 500-700 years as countries started to form and walls were strong enough to stand for years were made.

then 1600BC was where science prospered and the arms + space race started

electricity was something that people always knew, but it was named "electricity" in the 1600s by a scientist but it was only until the 1800s that scientist started fiddling with batteries and then finally in the late 1900s, electricity as we know it was finally invented.

this is probably the "50 years" your history teacher is talking about.

that said, technology has more or less stalled again because we...just dont have enough materials or elements to bring further changes.

that's why we built the LHC which is to discover new elements or create new ones.

but yea, most of the progress we've had so far are only computer stuff like AI and processing power which too, has stalled.

intel said in the early 2000s that theres just no way to increase processing power in an affordable way which is why they are just making cores and more cores and everyone is of the same view