There's not much the new engineering team can contribute. The old engineering team has years of insight and expertise actually generating profit with old but reliable technology. The vast majority of the new engineers / leadership come from the same outside company and their whole expertise is Kubernetes + AWS.
Yes, great tools, but they have shown they're not good problem solvers. Case in point, they decoupled the CMS and made it headless and the new headless frontend is an archaic management nightmare. They have to manually import pages every time there's a change via excel sheet, and it takes up to an hour to reflect new changes published from the CMS. Nobody who's been here for a while is happy because the new system absolutely sucks, and they're trying to pretend this is fine.
I don't think that attitude would help anyone: you are looking for positives, not for negatives. Calling them "not good problem solvers" won't help either — most engineers I know are mostly hampered by trying to appease stakeholders with conflicting requirements (or at least requirements in tension with each other). As I said, you need an honest, no-blame discussion to really bridge the gaps between the teams.
If I may suggest an easy read, look up Radical Candor by Kim Scott.
If "nobody who's been here a while" is ready to open their mind and embrace the new team members either, you are getting nowhere quick: hopefully this is not a battle, and you only come out a winner together.
Yes, great tools, but they have shown they're not good problem solvers. Case in point, they decoupled the CMS and made it headless and the new headless frontend is an archaic management nightmare. They have to manually import pages every time there's a change via excel sheet, and it takes up to an hour to reflect new changes published from the CMS. Nobody who's been here for a while is happy because the new system absolutely sucks, and they're trying to pretend this is fine.