Can I change my rear cassette to get lower gearing?

[emily_in_nc]

MTBs, these days, are even moving away from doubles to 1x systems with only one chainring in front and no front derailleur.

Interesting! I love that idea. It surely would simplify things. When I was riding hilly MTB trails frequently I found I stayed in my inner/granny ring on my MTB most of the time just so I could avoid shifting errors when the terrain got crazy and ever-changing. I would much rather coast downhill but be able to tackle pretty much anything uphill than get stuck unable to shift fast enough to handle a sudden steep climb after a descent.