Nope, I was actually always on par or even ahead of the AI in tech. Its pretty hard for them to get that tech lead when their cities are constantly being burnt to the ground. Plus I was allied with every single city state on the map with full patronage which gave me a pretty good boost to science (many cases because I liberated them). Plus liberal use of tech treaties as well (had to do something with all that cash I got from razing cities).
In the few instances where they were slightly ahead of me it didn't matter much. Its not too hard to win if they are only one unit type ahead of you, especially if your units are veterans.
I was constantly at war throughout the entire game (I never declared on them though they always attacked me first) from about 1000 BC to when I finally got the cultural win in the late 1800s. The problem was I wanted Bollywood so I couldn't actually finish someone off and take their capitol. I would raze them down to one last city left and then make peace. Then their neighbor would attack me and while I was kicking his butt the original one would rebuild and then decide to try me again. Somehow I became the bloodthirsty warmonger when I was just defending myself

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This was on Deity standard size map (well I think it was standard, I used random map settings but it looked like a standard map) by the way.