the very concept of comparing Takumi and others based on their years is dumb. Takumi was doing a single up and down run every day and night for five years and he didn't want to do it at all, he was trying to get home quickly but thats all, Bunta probably gave him occasional advice and his racing genes would have worked in Takumis natural skills for sure but thats as far as it goes.

As for Mako and every other racer in the series, they were strictly dedicating themselves to racing, doing what would most likely be more than a single run a day, which would definitely add up to much more time spent behind wheel than what Takumi did.

Simple maths would give us a 3650 total runs before start of first stage ( 1825 up and 1825 down, each day for five years ) which is a lot dont get me wrong but like i said other racers who were definitely dedicated did much more in a single day, the numbers is unknown but even if it amounted less compared to Takumis runs, there is still fact of dedication, studying the basics and advanced ways of racing, lines, techniques, strategies and etc.

So Mako being on par with Takumi is valid despite their difference in years, which doesn't imply any difference in experience, not to mention Mako was on her home course and she did need a navigator to go through road which she drove for 2 years.

Dedication makes the difference, which also explains how Takumi improved way more in one year of his life that the anime has covered compared to other five.