Beginning with Everson (mainly), the left took activist aim at their goal which resulted in Lemon. Lemon is simply a leftist interpretation of the First Amendment, nothing more.
When I have time I will trace the history of the Lemon test and display its leftist lineage for all to see. This has been done before in many publications and like I said, legal conservatives have always known Lemon to be the culmination of a leftist wish list.
The ACLU, Larry Tribe and all those who agree with judicial activism through an oligarchy, loved the Lemon test, it was their leftist dream come true.
As far as precedent was concerned, Lemon ignored most legal history and relied almost entirely upon very recently created precedent that had itself ignored precedent. The only precedent it relied upon was precedent created by pure leftist activism beginning largely in the 1940s.
You may be right. I haven't studied the matter. On reading Lemon, it seems to be based on precedent, at least to a far greater extent then Roe. If it relied on relatively new precedents, well, that's not necessarily the worst thing in the world.
As long as legislatures and school boards do things that touch on the sensitive subject of religion, the courts are going to be called on to see if the state action is Constitutional. These cases can be subtle. The court needs some rules for dealing with the First Amendment. The Lemon test doesn't strike me as wildly outrageous. State action should, for example, have a secular purpose. Who would disagree? The principal or primary effect of a state action must be one that neither advances nor inhibits religion. Again, who would disagree?
The third prong of the Lemon test seems a bit ambiguous -- the state action must not foster "an excessive government entanglement with religion." Lots of room to wiggle around there. Applying it can be tricky. The devil is in the details.
The First Amendment is a good one. It keeps the slimy hands of government out of religious matters. That leaves religion free. Who would disagree with that? I can't imagine how botched up things would be if the government schools, which are entirely incompetent, bloated, corrupt, and generally worthless, started meddling in religious matters.