You can get great results with both WordPress and alternatives, it really depends on how well you're handling things. WordPress can absolutely work, especially if you're careful when choosing plugins and themes, and set up proper caching, SEO, etc.
I've seen a lot of well-positioned WP websites, as well as affiliates who struggle with performance, bloat, and missed updates. That's actually why I built a custom CMS for affiliate sites, to try and address those issues. Not trying to replace WP for everyone, but for people who want something more focused, it can be a good fit.
https://dinomatic.com/gambling-cms - another option in case anyone here is exploring alternatives.
dinomatic.com → WordPress Themes & Plugins for Sports, Casino and Forex Affiliates
tablrr.app → Centralized Listing Management and Automated Sync for Affiliate Marketers