Couldn't agree more with the above. Or maybe I am somehow doing all of it wrongly? Just yesterday, I burned half a day trying to find available tickets to redeem because some of my 5xxk miles is expiring soon. First, try to fly to venice, but can only confirm 3 tickets out of 4 for family. Tried Athens, then Prague and finally found something for Moscow. And I am only looking at 2020 june holidays and not Dec. So I am already booking way in advanced, but still had to jump thru many hoops and loops. I think I stick to cashback.
What class of service were you looking at?
Maybe way in advance for you, but not for me. I usually book when they just open up for booking. So for today, they open up 24 or 25 July 2020 (ie about 330 days in advance) for reservations, then I will book my inbound flight at a later date, when they just open up. Now is about 1 month since SQ opened up for redemption (for June 2020), and you are looking at European destinations during Singapore school holidays, I'm not sure if there would be plenty availability left.
I do see 4 seats available in business for Venice on 24 July, via IST. The destinations you are looking for (other than Moscow), I do not think SQ flies direct. This, you also have to look at partner availability, not all airlines release seats at the same time, which may be the issue. For example, I booked SIN - FUK - HND - SIN, where the FUK - HND is on ANA. ANA did not open up 330 days in advance, and I can only ticket after they opened up like 250 days (or so) in advance. So if you are looking at partner flights, you will need to do some homework on when they open up (like LH only opens up premium cabin like 2 weeks before departure date).
Editted: I just anyhow put a date in for June 2020, and it shows 4 seats in business class to Venice, what were you looking to book, that you are complaining about?
Feel free to PM if you do not want too much of your information in public.