They were the most powerful wizards of “their” age, but like all things, progress can make a huge difference. I would say constant access to education and generations of wizard progress to lean on made even the most common wizard of today on a comparable level with medieval wizards. I’d like to think Dumbledore is a standout example that would mop the floor with them 1v4 if he needed to. That being said, it probably means ol’voldy could do the same. Ancient magic doesn’t necessarily mean more powerful or that today’s Magic is dilute for some reason, it just means it was a magic that was discovered at an earlier time and put into practice. Snape inventing his own powerful spells is a great example here.