Well I can't speak to the comparison, as I have no clue how much of DC's output was...well...out when Ultron was released. However given they only have what, 5 movies total at this point, compared to like 20 MCU's, I think the statement isn't without some merit, at least from an opinion standpoint.
I'm not a huge fan of the MCU these days either, as I find them very hit or miss, depending on the individual film. I also only ever saw MoS and Wonder Woman, because I thought BvS looked like arse from the start, and I've never been a fan of the " who would win in this fight?!" crap that is so prevalent in comic fandom. It gives me too many flashbacks to the White Wolf: World of Darkness pissing contests where people would do similar shit of "My vampire would totally kill your mage" "BS, my mage would totally kill your vampire." "Pssh, my werewolf would kill you both" "nuh uh, my vampire would totally do X thing and win." "My mage would counter X thing with Y thing and win." blah blah blah. So the second I saw that was the plot of the film, I lost what little interest I had. And Justice League looked equally bleh to me.
At best, for me at least, most Marvel movies fall into the "it was fine I guess" category, with a few of them being really good, or really bad (I'm looking at you Antman and Dr. Strange).
Where as DC has 1. put out way less films, so their quality doesn't average out as easily. and 2. I really only like Wonder Woman, which was genuinely good and fun, and something I would watch again any time it's on. MoS I'm happy to never see again, because like Ultron I really just don't remember anything from it, other than a vague "it was really annoying and frustrating to me. (though not for the most common reasons fans have). And the others are just not something I care to see. They just didn't look like something I wanted to spend my money on.