Mauer's 2009 season netted a 172 OPS+, an MVP, and 7.7 oWAR (BRef). In 2018-2019, Yelich posted back-to-back 164 and 179 OPS+ marks, with 7.3 oWAR both years. For their careers, Yelich is currently at 132 OPS+ vs. Mauer's 124.
It's an interesting comparison. Mauer's MVP season featured 109 games at catcher, so that's gotta be considered. Mauer hit 140 in OPS 5 times in his career--his worst mark was 98 (Yelich's is currently 99).
A lot of the gripes about Mauer I can recall from my time in the TC revolved around 1) the injuries you mention and 2) the size of the contract as an impediment to other parts of the Twins' roster.
As I look into this, there are some eerie similarities. Mauer hit 28 HRs in his MVP year and never got half that for the rest of his career. Yeli's hit 80 HR between 2018 and 2019. He's at 81 in all other years total, including yesterday's grand slam. The biggest difference is that Yelich posted two dominant years instead of one, and Mauer played a premium defensive position for 6-7 years.
It's weird, but I think Yelich's legacy in Milwaukee will depend on the team as a whole. Nobody's going to care about his contract if he puts up a 120 OPS and the Brewers' pitching leads the team to a World Series. I think the subset of anti-Mauer Twins' fans would've thought differently had they been able to turn all those division titles into pennants. Probably unfair, especially since Mauer is a more-likely-than-not HOFer at the end of the day (though the batting metrics are honestly a little underwhelming by Hall standards), but that's the game.
I'll say this. I think Yelich is a more dangerous offensive player and by a reasonably clear margin. For the last 5 years of his career, Mauer's OPS+ was like 105 at 1B/DH. In 2020, Yelich was at 110 in 58 games. I doubt Yelich gets to 170 again, but if the guy hits for any power at all, his walk rate and high OBP are going to push him into really good offensive territory.