I would complain far less if Gurriel or Chapman were to bat leadoff vs Tapia but neither of them is a very good choice for leadoff as they simply haven't been able to find their way onto base with any regularity. Perhaps over the course of an entire season Gurriel and Chapman will each have better numbers than Espinal but that's not the case for the season as a whole. If you go back over the last two seasons Espinal has the best WRC+ of the three at 114, Chapman is at 101, and Gurriel is 106. The numbers don't really back up either Chapman or Gurriel clearly better hitters although to be fair Espinal didn't necessarily earn his numbers last season and Gurriel is super streaky and hasn't hit his yearly hot streak yet.
I tend to think lineup construction should be a bit dynamic based on who's hot and who's not. Guys like Springer, Teoscar, Vladdy etc. can be more or less locked into place based on the quality of at bats they tend to regularly have, but everybody else should be shifted up or down as needed. If you look at the last two weeks Chapman has an OBP of .218, Gurriel is at .259 and Espinal is at .347. One of these to my eyes is a far better leadoff choice than the other two for this reason alone. Espinal has outperformed each of these hitters by most objective measures and his expected stats back that up as well. Among the regular starters he's produced the 3rd best WRC+ on the team and to me it makes sense to get him more at bats and not bury him at the bottom of the lineup on days when Springer is unavailable. There's no way Tapia should ever be receiving more at bats given what we've seen offensively from each player so far this season.