Technically, I could. Thanks to the widespread availability of (free) CAD software and associated calculators and the availability of the information about bridge making, I could make a bridge or a sky scraper. It would be horribly over-engineered but it would meet current code and probably be both the most expensive, least maintainable although most reliable bridge in the world. It would also take me a few years.
I actually just engineered a fire sprinkler system in my home, totally up to code as verified by our city's architects and fire engineers. It's also horribly over-engineered (too many sprinkler heads, bigger pipes, unnecessary valves and gauges, plenty of leftover capacity) and it took me several weeks just to get the drawings and calculations out but it saved me personally $7000 (a professional install was quoted at ~$8k, I did it for less than $1k).
If you want horribly slow software that is very expensive to maintain but also very robust, you can give the tools to a newbie with the willpower to do it and you would get something, eventually.