And why genre doesn't have to matter as much as you think it does within the realms of production.
I find a lot of producers, mixing engineers, and recording engineers like to carve out genre niches for themselves. Often times, this is due to stylistic preferences. If you like metal, why wouldn't you record, mix, or produce for metal bands? It is a lot easier to work with music if you enjoy the music, especially if you are going to be listening to it over and over.
If you like a particular genre of music, you likely also are already familiar with production tendencies for that genre. You know instinctively how the snare drums should sound for a punk band if you listen to punk. You have a general idea of what the space a saxophone should fill in a jazz record if you listen to jazz. That is not to say of course that there is only one way any of these instruments has to sound in these contexts, but there is an inherent understanding of what the recording should sound like finished, in order to 'sound like the intended genre'.
Especially for newer engineers, I think there is a lot of value in trying to work with genres at the very least more on the periphery of your musical tastes. If you mostly listen to indie folk, but can get into some deeper country, try mixing some! See if you can get into a project! You will likely find that the resulting sound is different than other recordings in the genre. It will stand out, but will still be identifiable as that genre.
Of course, more extreme genre jumps can be a lot of fun as well, provided you will still have a good time. Personally, I LOVE when metal bands find pop producers. A lot of the sensibilities from pop music can make for some great records. This is a common example that others I've spoken with like to cite as well. But what happens if someone who primarily records blues mixes a techno project?
The bottom line is that all genres tend to have differences in terms of how they are produced. How each instrument is handled, the space it is allotted, transitions, textures, reverbs, delays, etc. How big does the bass sound? Is it meant to play a supporting role, or is it accenting another instrument? Does it need to be distorted or saturated? How compressed does it need to be?
If you are looking to improve at your craft, having a greater breadth of knowledge of techniques can be a huge boon. And the records you will be able to create having gained knowledge from techniques learned my mixing other genres will allow you to vastly improve both at your 'home genre' and at any new genres you work with in the future. Innovation within the production side of the music industry plays a big role in the evolution of music. By expanding your toolkit, and using tools from one genre within the sphere of another, you will be able to make some unique records that sound great, and stand out.
The one caveat to this mindset is that the artists you are working for do have to consent to having a record that sounds different. Artists often have an end goal in mind. I have found consistently artists want to fit in within the genre. The more experience you have with mixing techniques across genres, the more tastefully you will be able to apply them. Even working with a new genre, the basics of mixing are the same. EQ, compression, saturation, and spatial effects. Selecting elements of the mix to draw to focus. Evolving the focus of the mix to keep interest. Balancing the mix so everything can be heard. The only thing that changes across genres is how you achieve balance, tonality, and what you choose to focus on.
If you want to, you can hop into a new genre quite quickly and be quite successful in achieving 'the sound' of the genre. If you immerse yourself in the genre for a few weeks, get accustomed to the different aspects of the mix, you could likely produce that genre at the same level that you produce the genres you are more comfortable with. However, if you are in a new genre, and you don't immerse yourself completely and try to hit 'the sound', that is where you can merger your knowledge with the new material and create something new.
Regardless, I think exploring genres is both a valuable exercise to improve your skills in music production, and can also help find a new sound within a genre. A thrash band is still going to be a thrash band if a hip-hop producer gets their hands on the multi-tracks. But couldn't that just be one cool sounding record?
Don't box yourself in and have fun exploring!