I assume you mean Timed Quests as they are called in-game
Not sure 'fun/engaging' are the right words, but they are a valuable addition, something to do and focus on, along with looting, medals, completing Achievements, etc
The list could be a bit longer and varied, seems to run out and repeat a bit quickly.
The list seems to be universal - everybody from Stone Age to Industrial gets the same quests, which makes some laughably easy or impossible depending where you are in the game - it's like they got put together in a design meeting and nobody actually tested them. 'Gain 100 medals' is a doddle if you are down at 200 medals, nigh on impossible if you're anything but French & 1800 medals.
Two that stick out as extreme are:
Build 35 tactics in 36 hours, which as each one takes 45 minutes, means being logging in every 3 hours just to trash 4 tactics and rebuild them.
Hire 45 mercenary armies in 24 hours (or maybe 36), again it would take a colossal amount of trade goods and reckless play to get them built & killed.
One that could do with tweaking is 'Train 1000 troops' - really needs to be troop spaces, nobody is going to suddenly switch to 100% foot troops just to do it.
The above should apply to the Troop Donate/Receive too.
Overall they are good and actually work