This issue has been debated to death in the 2K forums as well.
I also do not like the Pike to Lancer upgrade for several reasons.
First and foremost, the pike is the
default infantry unit of the Medieval era. Longswords are a resource unit and are supposed to be specialized at capturing cities. The default infantry unit of one era should upgrade to the default infantry unit of the next era (Ancient being the only exception, as the Warrior and Spearman are both "default" units). Thus, the pike (as the default unit of the medieval era) should upgrade to the musket (as the default infantry unit of the Reniassance). You should not have to build an entire new defensive army just because you entered a new era. If that's what they wanted to do, then nothing should have upgraded to the Musketman, and Longswords should have upgraded to Rifles (as in vanilla game). Or muskets and rifles should require a resource (i.e. saltpeter). If the devs want spears/pikes to be a specialized unit, then they should reduce their base strength so they aren't as competitive against warriors/swords and aren't practical for use against an invasion force, then introduce a NEW classical/medieval infantry unit (i.e. a axe/mace) that can act as a resourceless-default unit.
Secondly, the jump from foot unit to specialized mounted unit back to foot unit then to helicopter is jarring.
Lastly, the civilopedia says that the invention of muskets and bayonets obsoleted pikes and spears. So there
If you ask me, the upgrade tree in general needs some work.