The problem is that it's much too thin and therefore hard to read on computer screens. I'm sure it looks great on paper printed with the old Xerox laser printers that were around when it was made, but in its current form it's just way too thin to be read on a screen.
Someone on a German forum made a wider version of it which (imo) looks much better [1].
I strongly agree on the “too thin” point. On screen I find it an awful font, almost as bad as half the 300-weight sans-serifs too many people love to use on their websites. Computer Modern does look better printed, especially on less-accurate printers that thicken what they print.
Related: the serif font Equity comes in two grades to compensate for such types of printers (though both grades are thicker than Computer Modern), and discusses the rationale for this feature: https://mbtype.com/pdf/equity-type-specimen.pdf#page=5
Chrome & other browsers have had PDF reading capabilities for a long, long time. I actually can't remember a time when you couldn't view a PDF inside Chrome/Firefox.
My recollection is that Computer Modern didn't look very good on old laser printers, as their resolution just wasn't high enough to handle the detail of the glyphs. It was crafted for digital phototypesetting systems with a resolution of 1200dpi or more, and 300dpi laser printers couldn't do it justice.
It depended on the laser printer. It's funny that the poster mentioned Xerox laser printers in particular because cm looked especially bad on them: There were two competing approaches to laserprinting. One was write black where a laser was used to add charge to the parts of the drum that should be black. The other (used by Xerox and perhaps others) was write white where the whole drum was charged and the laser was used to remove charge from the parts that should be white. In either case, the pixel was a little bigger than the actual 1/300in x 1/300in square that was to be drawn so it resulted in CM coming out even more spindly on write white laser printers. Neenie Billawalla came up with a modification to the MF source code for CM to allow for increasing the darkness of the fonts as well as some other fine-tuning. (https://tug.org/TUGboat/tb08-1/tb17billawala.pdf)
As I recall, there were occasional other issues with running MF on the CM sources at low resolutions and it was often necessary to just tell MF to continue at the error prompt to generate the font (when Tom Rokicki's dvips incorporated auto-running MF to generate missing PK files for specific resolutions, I think it ran it with a default setting of ignoring errors).
Those 1980s Xerox laser printers were real beasts. The 87xx/97xx series printers were prone to rolling over (crashing) on TeX print jobs since downloading fonts to the printer was not fully supported. The first dvi driver for the Xerox printers actually required pre-installing font sets on the printer and only certain combinations of fonts could appear in a single document. I don't think the 27xx series printers were ever capable of handling TeX output.
The heavier version looks better, but this involves messing with Metafont, which generates bitmaps. (And sadly his sample PDF links have died.)
I don't know of a way to heavier outline fonts. I believe the commonly used versions aren't in fact derived smoothly from Metafont, but either fitted to the bitmaps, or drawn by hand over them. That would have been a good time to correct this sad mistake.
Related: the serif font Equity comes in two grades to compensate for such types of printers (though both grades are thicker than Computer Modern), and discusses the rationale for this feature: https://mbtype.com/pdf/equity-type-specimen.pdf#page=5