Just my 2 cents, Trials (LoR, LoRNM, and JV to some extent) FORCE objectives to be completed in a specific order, hence the team must coordinate efforts in order to get it done.
The most cooperation regular missions do to force coordination is the 2 panel friendship door, and 2 people at extraction to start the time. Otherwise 4 ppl can do their own thing and be off in their own world to complete the mission.
The current eidolon teralyst is a joke in terms of forcing coordination (note my use of coordination and not cooperation) in order to complete.
The current eidolon teralyst does require cooperation when pushing the number of captures a night.
However I am very sure veteran players regularly solo capture as many or possibly even more teralyst per night cycle as some 4man groups.
If DE intention is to make Trial Arcanes more accessible, they could have done many little things over a very much extended period of time in the past to promote the existence of trials.
I will concede however that in game resources are lacking to facilitate the learning of Trials, hence they do have a high barrier for entry for any new group of less than 4.
However the same can be said of many aspects of the game (damage buffs, multishot, crit and status definitions) and "go check the warframe wiki" is a common enough response. (the warframe wiki is listed in the fansites iirc)
I do however enjoy the trials and have friends that feel the same way. If some people are locked out of a game mode that I find enjoyable, so long as I have my fun I honestly don't care.