I love excalidraw, but I have to agree. It also looks very unprofessional so if you ever have to write customer-facing diagrams, you have tool fragmentation. I just stick to draw.io now (aka diagrams.net)

Why does it cause tool fragmentation? You can change the font to a normal sans-serif font or to a monospaced font.

Personally I like the default font. It looks weird to have my crappy doodles next to a normal computer font. The default one is very legible but has a style (and ligatures) that make it feel not too neat