That's likely due to HiDPI displays. A regular display is probably in the 100 DP...

Shoue on Nov 21, 2019 | parent | context | favorite | on: Slack’s new WYSIWYG input box is terrible

That's likely due to HiDPI displays. A regular display is probably in the 100 DPI range, but we have phones that are in the 400 DPI range, so that icon size suddenly isn't so big anymore.