Man coverage is not weak, and 3 steps is HUGE in the NFL. Watch Sundays games. The Eagles are almost excusively in a zero man or cov 1 scheme on passing downs, the Ravens play cov 1 5 man pressure defenses with Ed Reed free and the Steelers play single-high robber with Polomalu as the robber maybe 1/3 of the time with 3 under-3 deep zone blitzes with Polamalu either involved in the blitz or as a middle robber a large percentage of the time. The Patriots and the Giants almost are always in some sort of man coverage on the edges, or the Giants were last year, I saw them playing quarter-quarter-half-man a bunch this year. The Redskins it seems are always 5 rushers-cov 1 with Landry high. Man coverage certainly isn't weak, and is probably the most oft-used coverage in the pro football, even though the pundits would tell you its Tampa 2, which really isn't cover 2 at all.
As for the Mannings, much is overblown about this, as most teams utilize a check-with-me system on a lot of downs. Peyton is given more freedom, and more checks than most, and with good reason. He really has a knack for noticing sublte nuances that tip of a defense's plan before the snap. Its hard to even pick this stuff up watching film, much less watching the too close tv pictures. But don't kid yourself, all NFL teams use cwm in the run game, with pass protections, and most qb's have the ok to check things in the pass game as well.
And don't forget all those teams who run some of the run and shoot principles, the whole basis of that system is to read defenses on the fly and adjust routes to combat those coverages. For what your calling a "hot route," this is an example of one happening post-snap.
At the risk of getting long-winded, I thought maybe I'd clear up the term hot-route anyway, its one of my pet peaves. In coaching and playing circles, a hot route is really an underneath type route that the qb can get the ball to quickly if he's pressured early. These routes are built into the pass concept. A "sight adjustment" occurs when a rec. breaks off his route to attack an area that's left uncovered by a blitzer who will not be blocked. Most pro-style passing attacks have a built in hot route to one side of the concept (the front side) and a possible sight adjustment to the backside.