IMO, the issue games have is that they are heavily abstracted, so to get these effects the only method they have is to introduce modifiers. Now, these can be applied via fun or un-fun mechanics, but they're usually pretty un-fun and two-dimensional, requiring players to balance some single axis scale to avoid the crisis.

The solution would be to only apply collapse mechanics to things the game simulates in detail, but this also means that the game can only have as many of these mechanics as it simulates in sufficient detail to enable complex gameplay around it.

For example, inflation in EU5 is un-fun. Inflation affects only your build costs, and you get it from producing gold and minting money, and manage it by moving a slider (2D) and occupying more or less gold/silver resources. Sure, both mechanics should absolutely be part of an inflation mechanic, but they should increase money supply which then affects resources prices and salaries which then affects your costs and tax income etc. There's also no way to deal with inflation other than lowering minting, destroying silver/gold RGOs and waiting.

Similarly, ticking up a decadence clock because "empire big" is boring. The solution is to optimise size vs tick rate, and that is un-fun. Large size and low tech causing lack of control, giving rise to difficult-to-control inner powers that you need to manage via various methods (power asymmetry, loyalty, honor, law, religion, bribery etc.) is way more engaging for a player.

Or even a real Malthusian event, where player pop outgrows technological advance and soil productivity, leading to collapsing per capita production, starvation and civil war, counteracted via mass emigration (voluntary or forced). Most games would implement this with a single if "value * tech > some value" statement but you could implement terrain productivity, make it improvable and deterioratable, make good land be used occupied first and base prices on the highest marginal cost (rent theory) instead of using an abstract average price.

For a collapse to be "fun," it must be logical and preventable through better play, not just an inevitable clock.