Desire demons were already random mooks in DA:O, though.
You bargain with many of them, talk, etc. Not exactly random mooks.
continent ending threats is an exaggeration. every single harrowing involves one. maleficars could summon them. facing pride was always a possibility for a company of templars. but i agree there was a devaluation of these threats in DA2 and 3.
Harrowing is a closed, controlled environment where they kill you before it goes uncontrollably bad.
And, I said
potential continent ending threat. Maleficars can summon them, and that's exactly what happened in the Mage's Tower with Uldred, but the demon took over. The only reason it was stopped was due to chosen one PC. If the pride demon was able to finish preparations, easily fight off the Templars, the effect of that could be as destructive as the first blight. Loghain even had a deal with Uldred (now possessed) for freedom.
DA:I wasn't devaluation, it was destruction. That pride demon in Uldred was one of the best directed scenes in DA:O, that cat desire demons with the girl in basement is classic desire demon and can be quite tricky to deal with and save the girl at same time, etc. It made for a decent chunk of missions in DA:O. Even regular fight encounters can get quite tricky on higher difficulties.
In DA:I they walk around doing nothing, waiting for Inquisitor to come slay him for +1 power points. I don't think there's any interaction with a demon other than the nightmare in the Warden quest (one of worst in the entire game). Even then, you don't bargain/talk, the thing taunts you and inquisitor auto responds.
It really makes DA:O look like a masterpiece in contrast. DA:I is the worst game I've ever played. It's more offensive than any shit russian jank I've had the pleasure of playing. It's the only game I use, if someone is an apologist or likes it, everything else they say is tainted.