[Note, this is about raster graphics displays. The situation with raster based text display is similar but different, see below the divider]
This source states that introduction of raster graphics display began in mid-1970s only after affordable semiconductor memory had become available on the market.
True. Alas, one could add some restrictions as raster was tried and done before.
Would it be at all possible to make a raster graphics display by using the types of memory widely available in early 1970s (ferrite, I guess)?
Possible? For sure. Core was fast enough and could be done large enough.
Economic? For sure not.
A raster display needs a storage cell for each and every possible dot to be displayed, whereas a vector display only need to hold two pairs of coordinates for every line that will be displayed. So for example with a diplay of only 256x256 dots, the bitmap will needs 8KiB of core. Doesn't sound much, but then again, in the 60s even mainframes started with RAM of similar size.
A vector display with the same 256x256 addressable locations needs just 4 bytes per line (two if connected) to be displayed- so a grapic with 100 lines (quite a lot on a rough 256x256 screen) will need less than 400 bytes, 1/20th of a similar capable raster display.
But already the very first (widespread, commercial) graphics display, the IBM 2250 of 1964 could address 1024x1024 positions. For a raster display this would mean the needs of one megabit or 128 KiB - keep in mind, the basic model 360/30 was sold with 8 KiB memory and expandable to 64, while the top end 360/50 offered 64-512 KiB.
A vector display in contrast needs for a 1024x1024 position display only 21 bit per data word (display list entry). So a list with 1,000 entries needs only 21 kbit or ~3 KiB storage. These 10,000 entries are good for anywhere between 500 and 1,000 lines on screen. already quite complex and about the same memory as needed for a 80x24 display (~4 KiB including format information).
With using vector instead of raster, memory cost was still a limiting factor, that's why Tektronix could position their storage tube based terminals (4002/4010 series) in 1969/70 as a cheap alternative. By using a storage tube virtually unlimited vectors could be displayed without any RAM to hold them.
So bottom line, it wasn't about technology but cost.
Oh, and on a side note, a vector display line is a line, no matter what angle, on a raster display it's mostly a flight of steps. So raster is inherent ugly. Another reason why vector displays kept being the device used for CAD way until the late 80s. A line was a line and any transformation (rotation, sliding etc) could be done qute fast, as the CPU didn't have to recalculate every pixel, but only start and end of each line, which is a simple 3D to 2D transformation.
Now, for text displays the situation was the same but different. Text is primary defined by the characters to be displayed. For 80x24 this means the need of 1920 character words plus necessary format information, so usually ca 3-4,000 words - words, because at that time using only 7 bit per character was a substantial saving. After having the text in (some) memory, it doesn't really matter if it's displayed as raster or vector. In fact, vector has slight advantages when processing as a character is read once, then displayed and done, essentially lowering speed requirement for RAM by a factor of 8-12. Also, characters drawn in vector again look better on screen than the pixelation a raster display offers. That's why mainframe systems still offered vector based text terminals up to ca. 1980, only to be replaced when raster based systems offered higher resolutions.