You need to grow top pitchers, very few FA pitchers work out.
Yankees - Happ (1 yr), Paxton (1 yr), Domingo German (2015 trade with Miami, BA#6 for Mia), Sabathia was signed in 2009, Tanaka was a big Asian signing (those aren't an option for the Phillies).
Dodgers - Ryu signed at 25 out of Korea (6yr, $36M) with 91 MPH FB, Buehler #24-2015, Kershaw #7-2006, Maeda signed at 28 out of Japan (8yr, $25M) with 90 MPH FB, Stripling 5th rd (2012).
Braves - Teheran, LA-2007, Fried (SD #7-2012, TJ 2014, throw in in Upton trade, Soroka #28-2015, Gausman 2018 trade from Baltimore for prospects, Foltynewicz, traded from Houston in 2015 (BA#3Hou)
Houston - Verlander (trade from Detroit 2017), Cole (trade from Pittsburgh 2018), Miley (1yr $4.5M), Peacock (2013 trade from Oakland), McHugh (2013 waiver claim)
Minnesota - Berrios #32-2012, Perez (1yr-$3.5M), Pineda (2yr/$10M), Gibson #22-2009, Odorizi (2018 trade from Milwaukee)
For the most part starting pitchers are obtained from:
1) the draft (Nola, Irvin) and LA (though surprised how few)
2) trading for pitching prospects (see Eflin, Velasquez, Pivetta, Eickhoff)
3) short-term FA deals, 1-2 years (been burnt by Morton et al)
4) trades for 2nd tier guys
5) trades for 1st tier guys (Houston twice, because they have a loaded farm system)
6) big money signings
Phillies already have too much money tied up in Arrieta and the bullpen (Neshak, Robertson, Hunter, Nicasio)
The farm system is too shallow for major trades
They lack the veterans to sell at the TDL for prospects (maybe Williams for an A ball pitcher?).
Klentak should use some of the money freed up in RPs to add low cost SP veterans this offseason for depth.
Otherwise, they'll have to develop their own.