In Chicago, I stand corrected in that the Telemundo affiliate shows infomercials while the Univision and Telefutura outlets do not. However, that's not until the hours of 12:30 am to roughly 5:00 am and they actually toss a 2 hour movie in there for good measure. So, it's hardly abusive - and it's unlikely to have any impact with ratings. Heck, our Fox and CBS affiliates probably air more hours of infomercials here during the course of a week as WSNS (TEL) does! What WSNS doesn't do is air infomercials during the day or during prime time. So that's clearly not the issue here.
The issue at hand (IMO) is a combination of Univision snagging the best shows and Univision being so adept at marketing the Latino audience. They also do a lot of cross-promotion amongst their various TV and radio holdings. Like them or hate 'em, Univision does a heck of a job serving their target audience - using all of their platforms. That's something Telemundo can't match at this point. At one point a few years ago, they posing more of a challenge to Univision; now, under NBC Universal, they are a joke.
Oddly, here in Chi-town, the Telemundo affiliate has a much better local news product than the Univision affiliate does. I have watched them both a number of times, and it's not even close. WSNS has the best Spanish language local newscast in this market. But, the lead-in and lead-out shows are so much weaker for Telemundo that those newscasts just don't retain the viewership. The local newscast on Univision is followed by a national newscast (both at 5:30 PM and 10:30 PM CT) that is better and more well received than Telemundo's early evening national newscast. It's not bad, but it lacks the "star" power of Univision's offerings. Including that socialist (self proclaimed) Jorge Ramos.