Everyone has injuries, about equally. There is no guarantee that those players will play well when returning from suspension, or be able to reclaim their former glories, or, at the very least, be able to play again regularly enough to the same standard, upon return from injury. You can't use things that did not happen to temper the reality of what did happen. Again, this line of argument reduces somewhere along the scale to, 'we have a promising junior and *if* they would have made their breakthrough in this month, then things would have looked very different'; or, even, if we 'had won the matches we lost, we'd be in great shape'. Which, whilst both of those are undoubtedly true, it's a complete non-sequitur.
The shape of GB tennis in January, by necessity, cannot suppose that players that did not play would have excelled in order to raise the overall picture. Those players did not play. Neither did Gabi Taylor, or Sam Murray, or Eleanor Dean.
Important to remember, I'm not measuring whether it's a good month by whether we sweep the WTA or ATP. I'm looking all the way down the pyramid; at all levels we were 'meh' throughout the month, with one transcendant achievement standing apart, supplemented by a doubles title for Emily Appleton, Heather's SF, and not much else. That, 'not much else', is not just in terms of making later rounds in events, finals, and titles, but by players for the most part not even reaching the round to which they were seeded, or to which their ranking and the opponents they actually met, suggested that they might make. Every match that GB played, as that is the true sum total of reflecting upon how we did as the nation in the month.
Now, you're never going to win every match that you're expected to win, or where you are the higher ranked player, and so on. But, you can make an intelligently estimated measure of the sum of all of those encounters and deliver a verdict on balance. Imprecise, and rough, but no one is asking for a data-driven justification for every point played - it's illustrative. Again, personally, one players glorious shining highlight shouldn't blind us from looking at all of the efforts of all of the players, that DID play, and, without prejudice, or malice, evaluating them objectively.

Everyone plays the same calendar, in the same locations. It is not really any more of an upheaval for any other European peer nation to get to Australia in the Winter, at the start of the season, then it is for us here. I originally picked France and Germany as comparisons. German weather is not so different to us. France ans Spain do have that going for them, true. So, OK, lets use Czech Republic, Slovakia, Belgium, Russia etc. instead. Measuring us against those nations produces the same general result, and that cannot be explained away by good weather.

Poor Nicolas, Pierre-Hugues, Caro, Kiki & company, they've done very well for it to be so diminished
Bet they care when it comes to Fed/Davis Cup though!

I watched Kiki win her match in St. Petersburg, her parents in the stands were certainly living every moment, especially as she closed in on victory.
Good for her to finally get a win. It was a good win, too. Domi played well, and Kiki had plenty of chances to sabotage herself again, but didn't. Domi's husband was even more stressed and anxious than Kiki's parents; living every point, and he would not make a good poker player.

In France do they not play a lot of competitive singles at club level as opposed to recreational doubles, treating it much more as a sport to be involved in than a recreation? CD?

Arguably some of their Davis Cup selections haven't fully respected doubles or sometimes more importantly for practical results quite appreciated how important doubles specialists can sometimes be as against singles stars who can turn their hand to doubles.