This part timer topic is overrated as fukk.
I touched based on if the whole Goldberg quick match thing works in 2017 but overall I really never saw any problem with part timers personally.
Fans still want to see these guys despite what the internet and vocal minority may throw your way. The internet as greatly swayed peoples thoughts imo anyway. People focus more on part timers and business senses than just watching the product. No meme can change the fact that Brock, Rock, Taker, HBK, Berg etc. are still in high demand.
So use them and utilize your other guys as well. You want more eyes on the show. Bring in new fans or old fans by association. I can understand if an entire show from top to bottom was Old guy vs Old Guy. But its not. its high profile, high demand matches that they build around. Problem is, 90% of the show and stars are uninteresting. This has been the WWE logic since 2011 with Rock. You got Rock back to help bring back the eyes. They pit him with Cena. Threw in Miz and Rtruth. CM Punk. Guys like Taker, HHH are household names and they start to cash in and become veterans and attractions. They pit HHH with guys from Bryan to Reigns. Brock came back. Worked with alot of guys. Sting came back. Worked with Rollins. Goldberg came back. etc.
Then you say, well WWE needs to use these old guys to help build the newer guys by losing to them. IMO, that logic is overstated too. Full time booking and talent of said individuals matter more than just throwing old guys with new guys with hopes that they can just make a huge star. True stars are made from within the talent in the roster. Establihed full time guys are the ones who help make their peers into stars. The roles of guys like Cena, Orton etc is critical here. Like Austin helped Rock and vice versa. Or Mankind helped HHH. Hogan helping Warrior. List goes on.
WWE sucks at full time booking and 90% of the "new" talents just dont cut it. Plus its all a generational thing. Like it or not, alot of these guys today actually will be looked at as legends in years time. Brock was a beast in his 2002-2004 run but no one saw him as they do today until he left for 8 years and let his legacy build up. Let the time grow. I can easily see a guy like Reigns being one of the future part time stars. WWE just needs to build his way better. Rollins too. Orton will be and so will Cena. They could have Bray rolling if booked right, Much like Reigns. Even NXT has some talent waiting to shine.
In terms of today, the starpower is there somewhere but the part timers are not the biggest issue here.