None of these are good reasons not to field Infiltrators seriously .
Who here that is anti Infiltrators has used them in more than two games?
Two games is child's play
I think to fully understand a unit, let alone a list, you have to really play it into the ground. Jim Vesal had a great point in an interview on the Forge the Narrative podcast where he was discussing his awesome Daemons list with a guy on Facebook. This guy was running the exact same list, but had a question about handling Necrons, who he felt the list couldn't combat well. Jim was flabbergasted - in his experience, Necrons were one of the easier matchups! His advice - play another 30 games, understand the list, then come back for some questions.
I think that's good advice across the board. That experience helps you learn how to cover your weaknesses, and in turn the unit's weaknesses, during the heat of a match rather than constantly trying to theory your way to an answer in the list building stage. My few modest games with them haven't resulted in anything but a glowing recommendation from me, I do recognize that more time is needed. However, in my experience, sometimes things that look like cons on paper can turn out to be pros if you just shift your perception a bit...
For me...(shamelessly stealing Karhedron's list design)
Defense: I have found units using high damage or high AP weaponry like plasma on my Infiltrators is actually a boon rather than a curse. Anything that helps confuse target priority is valuable, and if the opponent is deciding to take on the 2w Scout troops with valuable multi-damage high AP firepower rather than something who's presence threatens their valuable units, I'm okay with that trade. This is especially true when it can become a bit of a trap by forcing the opponent to overextend those units just to deal with the Infiltrators. At the same time, the weaponry that clears scouts so easily can't do the same with Infiltrators, helping them contain the opponent for longer, where the helix also comes into play in providing more staying power. And it's also important to note that Plasma is deadlier against Scouts, but you often don't want to or need to use it against them. If you had a way to force your opponent to consider using plasma to deal with scouts, wouldn't you find that valuable?
Offense: Scouts win in number of bolter shots or bolter equivalent melee attacks, but that isn't worth much. Most lists are not missing out on bolter equivalent shooting. It's important to also consider that scouts can run with heavy bolters to give you access to another source of Hellfire shells, but given the much reduced durability, is it really worth adding more cost the unit?
Price: This is a component that I think is much more relevant to BA than other marine forces. BA likes CP - other marines don't really need much of it since there are so few valuable Stratagems to really rely on. Your mileage may vary here, but Karhedron is right that this is an important thing to consider.
Deployment: Ditto - same ability, but the difference is that this isn't isolated - it increases the value of the offensive/defensive points above.
Disruption: Specific to the Infiltrators alone, and while situational, it is certainly powerful. Turns off some specific strats entirely, including ones that you might use to take out 2w models like this in the form of rapid fire plasma dropping in, so it does have a bit of a defensive boon there.
Objective holding: Two Scout squads can certainly hold twice as many objectives as one Infiltrator squad, but combined with the above durability differences, how valuable is that really? 10 scouts will die faster and to a variety of more numerous weapons than 5 Infiltrators will after all.