My (not-a-lawyer) understanding is that a trademark is 'genericized' only when it's become so ubiquitous that its public use no longer refers to a single, unique source or origin of product, but to an entire generic class of products: escalator, granola, trampoline are some older examples of 'genericized' trademarks.

In this case, 'Bundler' still refers pretty clearly to a single brand-name utility within the Ruby ecosystem. However, the goods/services in the trademark registration application [1] covers "Downloadable computer software for managing, processing, optimizing, and organizing source code and dependencies", which is a broader class of services. The descriptive word "bundler" is quite widely used in the JavaScript ecosystem, for example, to describe this general type of dependency-management software (esbuild calls itself "An extremely fast bundler for the web", for example). I could certainly see the "Bundler" trademark being contested as a descriptive mark that hasn't acquired significant secondary meaning in that broader context, so it will be interesting to see whether this trademark application is upheld upon review (or potential opposition).

[1] https://tsdr.uspto.gov/#caseNumber=99407082&caseSearchType=U...