It actually doesn't slow you down too much.
If doing research, that depends on tech cost and research capacity. It costs more and more beakers the higher the difficulty level, and the bigger the map. Also, if you're self-researching everything ... VMXA has played a bunch of AW games... even if one trades by making peace on a turn, trading, and then immediately declaring war during that turn, which might not be AW, or trading on the first turn it's still more difficult research wise and you can't make gpt from selling tech, since you need military early, especially when the AIs have free units roaming about ... in a Monarchy, it's still a bunch of turns for many techs. Yea, Republic is better for commerce. But, if playing Always War, one might lose a city or two or three since one needs to defend more areas, and more threats come your way. The luxury slider might get used more sure, but if it gets steep, then either starvation or an anarchy is needed. And an anarchy means no more replacements for a while.
Sid tech cost is also very high, and I know VMXA has played some Sid. It's hard to express how steep tech cost can be if you haven't seen it. But, basically I can say that with rather powerful starts that I found using MapFinder, I could almost always have some culture build in my capital up to the midway through the industrial age. When I tried Sid using my capital I would run out of builds for two reasons: the AIs might beat me to something like Bach's Cathedral that I could usually hold off to later. Or because it took me so much longer to research for the techs. So, I stopped using the capital and started using the 2nd city, and it worked better. But, I had a good amount of palace pre-building going on.
Though, yea, if you're playing Monarch in a Republic with early tourist attractions, and some alright other cities, 5 turns sounds about right. Huge Monarch though... maybe not.
Anyways, hope I clarified both of your intended claims. I think they're both correct, just coming from different game contexts.