Given how close to the deadline the Merrifield acquisition was made I'm sure this was far from the first choice for the front office. It was definitely a headscratcher to move out Castillo given the lack of starting depth in the organization, but Taylor isn't likely somebody to lose any sleep over. The team didn't even protect him ahead of the rule 5 draft, and given the large number of prospects needing to be added to the 40 man roster this offseason it made a lot of sense to consolidate some of the more extraneous prospects into help for the big league roster. There was a pronounced need to attain outfield help given the tenuous Springer injury situation, so if moving out Castillo ended up being the only way to get this done then so be it.
You can certainly choose to call me a homer, optimist or whatever other descriptor you choose but I am a firm believer in both Teoscar and Gurriel offensively. If I recall correctly the only time Teo has really struggled since his breakout was this season after his IL stint. He's been one of baseballs best hitting outfielders dating back several seasons now and has several silver slugger awards to back this up. Gurriel is certainly hot and cold, however the hit tool is top notch and he appears to have settled into a new lower power high batting average approach. I don't see either of these guys presence in the lineup as an issue in the slightest.
Benintendi may have been a decent pickup, but it doesn't appear he can play center field anymore. It's a small sample size but he's struggled tremendously so far as a Yankee. Ian Happ wasn't moved at the deadline despite this being a true sellers market bringing back big returns, so the ask from the Cubs must have been pretty outlandish. The front office wasn't interested in moving out handful of elite prospects in the minor leagues this trade deadline, and without knowing what the asks were from other teams for more impactful lineup help it's hard to get terribly upset about the players who were brought in.