Here are a few workarounds for raster tiles [0]. You can either:

- limit the maximum zoom for raster tiles layers

- use higher resolution tiles (if they exist @2x or @4x)

- lower the DPI in Layout Settings -> Export settings (it should not impact vector layers)

- user vector tiles

[0] https://gis.stackexchange.com/questions/286167/qgis-gives-di...