Its not really fair to compare the hamstrung and manipulated (by the Fauj) PTI coalition that barely governed for 3 years, to an entity that has essentially controlled the levers of power in Pakistan throughout its history.
In fact, one of the more popular arguments used by Fauji apologists (to justify the overthrow of the PTI government), is that IK ‘refused to listen to the Fauji leadership about Russia and Palestine’. IK also fell out if favor for pursuing an Islamic bloc free of the control of the psychopath running Saudi Arabia … sounds like IK would have done exactly what the Fauji leadership refuses to do.
Since you used the word "apologists", let me be clear, I don't justify Fauji overthrow etc. (I have never said here that I am happy with the prevailing situation) nor do I justify IK's incarceration and believe he should be freed.
However, from a realpolitik standpoint, Imran Khan had the penchant of making calls with his trademark "I know better than everyone else" swagger. That has had negative implications for the country. In the eyes of PTI supporters, this was a minor sin, those across the aisle felt very differently. Perhaps it is a matter of perspective so I will leave it at that.
Coming to topic on hand, people can call Saudis all sorts of names, but in every dire situation, in a pinch, they have helped Pakistan financially, diplomatically more than ANY other country, perhaps except China. I understand that a significant number of Pakistanis have a very favorable view of Iranian clergy, but Pakistan has to manage its relations with countries that help further our interests. In the overall scheme of things, KSA has a higher precedence than Iran. We don't even do these things at Iran's costs as can be seen with untiring efforts by Pakistan to broker peace between Iran and the US.
As such, Pakistan has been able to do what has made sense for its interests. In 2015, under intense pressure from the Saudis and Emeratis, Pakistan did not enter the fray in Yemen. Why do we think Pakistan will do so now? The trilateral defense pact is defensive in nature, it means Pakistan will help solidify the home-front for the Saudis and that is what Pakistan has been doing and not just now, but since the early 80s.