Sure, but a modern computer also has orders of magnitude more processing power than devices that only ran a command line. There is no reason that we cant have both, except incompetence and/or bad economic incentives.
For example, properly displaying text now requires having a copy of at least the most important parts of the Unicode standard in memory. Things like knowing if a character occupies one, two, or many character cells are very important for even a simple text terminal. Word splitting, kerning, shaping, bi–directional text display, the number of possible refinements grows without bound and all of them need metadata about each and every character. Your average web browser has megabytes of the stuff just sitting around in memory so that it is ready as soon as a character has to go up on the screen. Older computer just didn’t have that kind of memory to spare.
If you want the old–school experience you can still boot straight into the Linux Console, which still thinks that there are only 256 characters. It seems to be reasonably snappy.
I suppose you could put a ton of OS and libraries in a (modern equiv of EEP)ROM for immediate access. The original Macintosh was kinda like that. But things went the other way when disk storage dropped in price a lot faster than chip storage.
Maybe we're back to a point where the former is economically viable, but there would be a lot of historic baggage to overcome.