I have a S&W 2.0 Compact, a Glock 43 and this January purchased a Sig P365. The compact is so much heavier it never gets carried. Its not the size,its the weight. The subcompact would be a couple of ounces lighter than the compact but still heavier than the P365. The Sig is close to the limit for how heavy a gun can be before I have to switch from a comfortable belt to a stiff, uncomfortable gun belt.
One of my main carry guns is 34.2 ounces (my SIG P229 chambered in .357 SIG which has a heavier slide than the 9mm). I use it with a minimalist carry belt from Langdon Tactical Technology that only has support where it's needed. It is thus the lightest belt I've used to conceal carry over the last 15 years, and it supports that weight of my pistol just fine (as an aside, my body weight can and does change more than that in a single day). Everyone is different, but that's why I personally can't take serious complaints against weight. It just doesn't affect me. I am sure it affects others, and that must be rough, but I am happy I can carry the weight because, all things being equal, a heavier gun is going to handle and shoot better than a lighter one. I'm not saying that extra performance is necessary in a concealed carry gun, it's not, but it's just one more example of how the P365 is a great gun, but there are better choices for some people like me as a G26, M&P Subcompact, P229, etc. are better shooters in my hands (as are most of my carry guns). I also know how it stacks up to carrying lighter guns because I also carry a much lighter gun than a P365 (my Ruger LCP II which is only 10.6 ounces). I don't carry it as much, but I have it for comparison.
No gun make is perfect but Shields have a great reputation for being reliable and durable. A smaller, lighter higher capacity but finicky and less reliable P365 competitor would be a mistake. If S&W does make a gun like that I hope they take the time to make sure it is every bit as reliable and durable as the current Shield. Given the problems I have had with my P365 I would buy one even if it was an ounce or two heavier.
I totally agree that if they change the Shield Smith & Wesson does not sacrifice reliability (which is never worth the extra capacity in my opinion). Personally, since I prefer carrying appendix, I wouldn't want anything shorter either. In fact, I prefer carrying larger guns because the longer barrels tend to work better with the wedges I put on my holsters to mitigate flagging myself.
As an aside, I doubt the geometry of the P365 magazine was lost on pistol manufacturers. That's a whole other matter, but it is too simple a technology for manufacturers to have not been sitting on it for years (if not decades), but manufacturers work together in my opinion to...well, I am going off on a tangent. All I will say is that if I owned a company like Glock, Smith & Wesson, SIG Sauer, etc., I would have fired my engineers thirty years ago if they couldn't bring me a magazine design that could fit that many rounds in that size of a magazine. It's not like some new super strong thinner metal was invented, and of course it's no coincidence that "Springfield Armory" (if that's what we want to call it) came out with an even better magazine design within a year or so. I wouldn't be surprised if Smith and Glock come out with higher capacity magazines that change their key subcompact pistols little (if at all).
Anyway, like I said, the P365 is a great gun, but as you alluded to, there are always sacrifices made in pistols, and while the S&W Subcompact and Glock 26 are bigger and heavier, they are noticeably better shooters in my opinion, yet they're small enough for me to conceal in any way I'd conceal a P365, and even better for the reason I mentioned. That said, everyone is different. Some people really need a smaller gun than the M&P Subcompact or the G26, and in those cases the P365 is a godsend that prevents them from having to give up little or anything in terms of capacity.
