The reason this thread never converges to a conclusion is because the answer is neither yes or no. Is retro faster? Sometimes it is, but sometimes it isn't.
Yes, modern is usually faster, but the question remains how much faster, and is the extra expense worth it? For example, my rigid Dynatech whch i could builf for 100 quid comes in at about 10% slower than a decent carbon 29er hard tail with 2x11 gearing which costs more than ten times as much. I'm pretty sure most of that difference is down to wheel size, while so called improvements like giant hollow bottom bracket axles, 1x11 grousets and carbon make only marginal differences, if at all. The supposed need for many modern bike technologies is hyped way out of proportion by the bike industry.
Something I find curious is the interest shown by industry shills on youtube (GCN, GMBN etc.) in doing dubious retro vs modern comparisons. It's as though the industry worries that people might wake up to the fact that this year's new range of bikes is no better than last year's. And even worse (for the industry), that people might extrapolate from that and start looking at older bikes that do the job pretty nearly as well as new bikes.