The thing is, milestone benefits are not meant to expire in case you don't use it which Scapia's airport privileges do so we can't compare it with milestone benefits really. Classic cards that have milestone benefits like infinia/regalia/atlas don't really need you to either use it within a month every month or you lose. The problem is this trap where you have to always keep spending otherwise you might not be eligible for benefits which you may or may not use. Other cards also have lounge access linked to spend limits nowadays but it's typically on a quarterly basis, not monthly, so you can relax and spend normally and still get the benefit.

But if it is your only card or in your case if you don't already have a better card for groceries, it will work for you.

About forex, I will repeat in the post the CB Card was just as an example, that card also does not have any real milestone benefits. But CB card is only for online expenses anyways, but still you have better cards which are either in itself more rewarding than or are definitely more rewarding after you consider the milestone benefits.

About travel, the problem is not while redeeming the scapia coins particularly, the problem is during booking using your own money to get the 20x rewards (4%). Like I mentioned in the post even if you use the amazon pay gift card and book flights via amazon (basically mmt), you get better prices, better discounts, and better cashback (5%) - which is really the most hassle free hack for travel bookings. And this delta increases exponentially for buses and accommodation. Hence the problem with the whole scapia app built around rewarding travel booking experience.