So let's take a DC 15 Con save. The 9 Con (-1) character saves on a 16 or higher. The 15 Con (+2) character saves on a 13 or higher. So 3 times out of 20, on a simple d20 roll with no other compensating factors (Inspiration/Bardic Inspiration/Bless/Resistance/etc), the modifier actually makes a difference. Is that something that we all truly notice at the table during any given play session? We might sense it over the course of a campaign but, surely many of us have witnessed this, a player (or other players) are more likely to blame the d20 itself than to blame any one choice of an ability score.
Fortunately, characters are not wholly defined by a single stat. When a low con character is created (that low score, after all, needs to go somewhere), some/many players will choose to mitigate that weakness through, for an example Warlock, one or more such things as: being a Hill Dwarf, Fiendish Vigor, Eldritch Mind, the Tough feat, the Moderately Armored feat, earning Inspiration, teaming up with other party members who can heal and protect, seeking out and carrying extra healing potions... etc, etc.
In the end, whether via array or point buy or (typically) 4d6, a character will have a "low" stat. They have plenty of options to mitigate against it somehow wherever it might be, if they so choose. I'm pretty sure, based on your ardent evangelism on the forum of "No One True Way" that you wouldn't really balk at someone else at your table creating a character with -1 to Con, right? What you've outlined above is just your preference for a PC that you personally would play, yes?