It's not faith, it's understanding that he is not getting opportunities.
Here is where MHJ ranks.
55th in the NFL in targets.
51st in the NFL in yards per target.
Consider this. Kyler has attempted three passes deep to MHJ. One was a 45 yard completion vs the Saints. One was almost a huge play vs the Saints. The third was a 38 yards pass interference. Those aren't outcomes of a bad or mid WR. Only an incompetent OC like Petzing wouldn't' emphasize this more.
These are two stats that are supposed to match up.
There are opportunity stats and there are efficiency stats. When an elite WR is being held back by a lack of targets, he will have bad opportunity stats and amazing efficiency stats. MHJ has good opportunity stats (targets, air yards, route participation) and mediocre/bad efficiency stats (yards per route run, catch rate, separation). Efficiency is how you're supposed to know a WR is good. Judging the player based on what he does with the targets he's given.
Elite WR1 like Nabers are super efficient and get a lot of targets. Low end WR1s, like Calvin Ridley, are not super efficient, but still can get okay counting stats through sheer volume. Often times low end WR1s are outscored by efficient WR2s. Right now MHJ is the WR2 in this offense. MHJ has a 20% target share, while McBride has a 29% target share. That is normal considering MHJs career yards per route run is 1.61 , while post breakout McBride's is 2.42. It is also an extremely high target share for a WR2, we have a very concentrated offense. McBride is the more efficient receiver and deserves the higher target share.
Last year MHJ had the 23rd most targets in the league, but his yard per route run of 1.68 was 57th in the league. He was a super inefficient player, and if he wasnt a rookie the obvious conclusion would be to reduce his target share. Through his first 2 games this year these numbers havent really changed. Peppering an inefficient WR with targets doesnt make him more efficient, or lead to elite receiving numbers. It would just improve his reputation with the fantasy community (points per reception), while tanking our actual offense. If Marvin starts turning his opportunities (of which there are plenty) into actual yards I guarantee you his opportunities will increase. I'm just as eager for a true MHJ breakout as anyone else.
If you're curious, a real example of an elite WR being held back a lack of opportunity is AJ Brown. Last year Brown had the 39th most targets in the league (97) and 2nd best yards per route run (3.16).