The convergence of UX and SEO is genuine and it does not eliminate the conflicts. It changes what they are about.
The old arguments have mostly resolved
Requests for more text, more keywords and more internal links used to put SEO against design regularly. Those requests were largely wrong and the discipline has moved on, which is worth acknowledging explicitly when working with a design team.
The remaining conflicts are about rendering and interaction
Content hidden behind interactions, infinite scroll with no crawlable pagination, and heavy client-side rendering are the real friction points. All are design and engineering decisions with genuine search consequences, and all have solutions that preserve the intended experience.
Bring evidence, not best practice
A design team will discount a general assertion and engage with your own data. Segment conversion or engagement by the pattern in question and the conversation becomes collaborative rather than territorial.
Be involved before the designs exist
Reviewing finished designs guarantees an adversarial relationship, because every finding is now rework. Contributing constraints during the design phase costs a fraction as much and produces better outcomes for both concerns.