It's a legitimate worry. It looks like we're very likely to get additional production from Gordon. I am very much not predicting he will bang in the fifteen he is currently on pace for. We were at 43 last season, and we look like we're slightly sub-40 on the merits unless Gordon really kicks on. Sub-40 is very chancy to stay up unless we defend like a top 6 side, which is an enormous if even with all the adds. We're defending at that kind of clip now, but we also haven't been pasted by City and Arsenal yet.
What actually bothers me more than the raw numbers is the fact that we got thirteen goals from odd places all over the pitch last season, as well as a bunch of set piece goals (some of which count in both categories), and we have none of those through five fixtures. Our scorers are Gordon (2), Gray (1) and Digne (1), and the last is a former player doing us a solid while cutting out Iwobi. We have the disallowed goal off a corner at Villa for offside, yes, but that's inexperience from Gordon in not realizing that he has to get back onside once it's clear someone else will have the first touch. Someone else is in that space if we have an actual striker on the pitch, and that someone else would instinctively know this. It's a sloppy point to bin off.
New players, OK, players out of position, OK, but we were absolutely reliant on that production last season to stay up. We aren't yet generating it, and if we don't start we're down unless the forwards and Iwobi ninja a bunch of goals out of nothing. That seems very unlikely, for the reasons you outlined.