The thing about such a format is that it doesnt allow for any sort of dynamism on the main plot. An example is Shakuras. No matter at what time you travel to it, the zerg never overrun it. There is never a tangible sense of stakes, because everything stands still until you interact with it. Contrast with the more linear and focused Broodwar or, on the other side of the coin, the hard choices in XCOM. SC2 storytelling method works well for a more sandbox esque narrative, but LotV states that you are short on time as amon is aggressively invading all the sector, which is why you dont do any sort of sidequests, and yet they allow it to pick the order you want to address the invasion.
No, that's only seemingly true. There is a scale from 'linear' to 'open' which any narrative can be placed on. Fully linear stories are found in some games, but mainly in books or movies, while fully 'open' games are sandboxes in which the player creates their own story, like Minecraft. Anything in between could be called 'interactive', in that the player makes decisions which somewhat impact the way the story plays out. This scale is solely a measurement of how much impact a player has on the events that happen, and how linear or open a narrative for a game is made is purely a stylistic choice (that is also bound by time and effort constraints). It's not true that a more open game is inherently detrimental to 'dynamism on the main plot'; take a look at The Walking Dead or Life is Strange if you want some examples on how a plot can be very suspenseful while still giving the player heaps of choice.
The issue is that it's just not necessarily approached well in LotV. I don't think it's done in a terrible fashion, really - there is still a sense of urgency through the campaign, even if you choose which hurdles to tackle before heading to Amon. That said, I'll give you that it could have done better. That doesn't mean it inherently couldn't work, at all, though. All the Shakuras arc needed was a couple of pointers by sidekicks saying "Shakuras are streaming into Zerg as we speak!", or even just an "Executor, the portal to Aiur has re-opened a couple of hours ago!" at the start of the Shakuras missions to explain why the planet isn't being swarmed while you do the other missions.
One thing else that could've worked in favor of blasting Shakuras is a mission where the player manages to destroy the Warp Gate to Aiur, but it's still not enough - Void rifts open and the Zerg/Corrupted Protoss/Hybrid from Aiur still pour through, making the situation nigh-irreversible - With a Warp Gate, you could blast it into oblivion, not only shutting the passage but also kill everyone and everything in transit, but how can you shut something that has nothing connecting it?
Something I can agree safely is that the destruction of Shakuras wasn't just rushed, but rather handled callously, poorly exploring Vorazun's character of her sticking to something she'd call a home (She lived there for too long, WTH?) as well as all the cultural/religious artifacts and traditions that the Protoss couldn't evacuate before Artanis went right into the temple. Also, that'd literally be the last option ever conceived, but she's apparently all like 'No, I won't fight harder for it, let's just blow it up.' :p