Host-pathogen interactions play out as a genuine, ongoing back-and-forth. The innate immune system's first line of defence recognises broad, shared molecular patterns common to whole classes of pathogens, rather than needing to recognise any one specific invader individually, letting it respond within minutes of an infection beginning, and many successful pathogens have themselves evolved specific molecular strategies to actively evade or interfere with exactly that recognition system.
Innate immunity recognises broad patterns rather than specific individual invaders
Specialised receptors in the innate immune system detect molecular patterns common across broad classes of pathogens, a shared bacterial cell wall component, say, rather than needing to recognise any one specific pathogen individually the way the adaptive immune system eventually does. That broad, pattern-based recognition is exactly what lets the innate response act within minutes of an infection starting, rather than needing days to develop the way a pathogen-specific adaptive response typically does.
Successful pathogens have evolved their own countermeasures against that same recognition system
Many successful pathogens have evolved specific molecular strategies that actively interfere with, or actively hide from, a host's pattern-recognition machinery, disguising their own molecular signatures or directly suppressing the host's resulting signalling response. That's a genuine evolutionary arms race playing out continuously at the molecular level between host recognition systems and pathogen evasion strategies, each side's adaptations shaping what the other side needs to do next to keep succeeding.
What we're still unsure about
That innate immunity relies on broad pattern recognition, and that many pathogens have evolved specific evasion strategies against it, is well established, extensively documented microbiology and immunology. What's genuinely still an active area of ongoing research is that exactly how a specific pathogen's evasion strategy actually evolved, and how effective it genuinely is against a given host species' particular immune recognition machinery, has to be worked out case by case rather than predicted from any general theory, since host-pathogen interactions are highly specific to the exact pairing involved, and microbiologists continue to discover new evasion strategies in specific pathogens that weren't previously known or understood.
This sits inside Immunology & Host-Pathogen Interactions, one of seven topics in Microbiology, one of six domains in Biology, one of seventeen subjects the app can quiz you on.