I mostly agree with the comments on the HfP post. The card has always had a 10k spend requirement, yet £10k in 2004 when it was introduced is worth about £19k today, so I do get the justification for the increase in spend threshold. The fee increase is harder to justify, as it has already had a recent increase in the annual fee from £195, and both coming together does feel like a big hit.
But the changes to account for inflation are only going one way, if we're paying a higher fee and having to spend more to get a voucher, so too should we be getting a higher earn rate, 2/£ would be more appropriate now, though I doubt Amex will do this. If they see droves of people cancelling I'm sure they'll rethink, but frankly I don't think they expect that to happen, and they're probably right.
I suppose the other thing which could offset the increase in fee is if there are more opportunities to earn TPs going forwards. Though (and I'm no expert) I would have thought that from a PR perspective it would make sense to announce those new enhancements first, then have a really amazing offering with the current fees for a few months, and then announce the increase in fee to offset it. That way you can justify the increase more easily, and you also get a wave of subscriptions when the enhancements come, but while some will cancel when the fees go up, most of them won't. So if my reasoning is correct, maybe we won't see enchancements like this coming, hence why they've chosen to do this now.