And why not set the limit for Platinums to 2 million points?

The issue here is not the number of each individual tier members but the availability of upgrades.
Zero availability for practically all longhaul legs 11 months ahead is hurting me personally a lot. I travel business for work and have not flown longhaul economy for ages and this lack of upgrade seats or late release of them will make planning my personal travel more difficult and I have actually switched some of my loalty to other OW carriers with paid J where I could have used part of my trip on AY.

AY has changed the strategy with upgrade space availability and prefer to sell airport upgades, on-board upgrades and whatever at horrible price levels on the expense of tier loyalty.
Opening upgrade space well in advance would allow customers to drain their voucher balance more evenly and well ahead. More options would distribute the demand more evenly.
AY should open 2-4 seats on longhauls well ahead and only then open up a waitlist for Plats (+Golds) and rest of the clientele.
Seeing a zero availability woud be an indication that most of the upgrades have been used already. All this would apparently mean change of strategy and AY's already inferior IT systems (with a cost).

I do not see a glorious future for AY tier member longhaul upgrades, sadly.