B737 Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 604; Flight Crew Type 11000
ATC Issue All Types; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Undershoot
General None Reported / Taken
Procedure
Too much traffic arriving at LAX at the same time. We were issued multiple vectors and speed reductions throughout the arrival. We continued to increase drag to make each restriction. The clearances continued to be 'descend via the IRNMN 2 except maintain xxx speed.' We were able to make all the restrictions until they issued a 170 speed; but offered no relief from the 8000-9000 feet restriction at JUUSE. We crossed at 9800 feet. I would have asked for relief and would probably have gotten it; but there was no break in the radio traffic. All the other aircraft were told 'do the best you can' which technically does not forgive an altitude deviation. It would be better if they stopped saying 'descend via except...' and changed to 'descend and maintain xxx; best rate down.'Change the clearance verbiage to include relief when issuing slower speeds on arrivals that make it challenging or impossible to meet the published restrictions.
B737 Captain reported being unable to comply with crossing restriction while on LAX arrival due to assigned speed restriction.