I'm not a fan of DRM, but I don't find this argument very convincing. It's pretty much impossible for anybody to create a new mainstream browser at this point. The standards are huge and complex and require seriously optimised implementations to get acceptable performance.

Which is why we only have a handful of competitive browser engines today, and all of them are based on code at least 15 years old. The last time somebody created a serious new mainstream browser (that wasn't just a re-skin of an existing one) was 7 years ago, and it was still largely based on existing code, despite having the backing of one of the biggest tech corporations on the planet. The standards have become vastly larger and more complex since then, and security and performance expectations much higher. Just keeping up with all the new standards is hugely expensive. The cost of a DRM module from Adobe is surely the least of your worries if you want to create and maintain a new browser.