Extract Values Following Specific Substrings in String Containing Spaces Using Awk

If awk is no requirement you could just cut string into substrings with grep,
replace colons with = and whitespaces with _ with sed.
The output could evaluated with eval to make it variables

WordPress version: 5.5.3 -> WordPress_version=5.5.3
Database revision: 48748 -> Database_revision=48748
TinyMCE version: 4.9100  -> TinyMCE_version=4.9100
Package language: en_US  -> Package_language=en_US

to make this work you need to differ variable names from variable values.
in this example this is done by len so en_US is treated as value

#!/bin/bash

# input string
text='WordPress version: 5.5.3 Database revision: 48748 TinyMCE version: 4.9100 (49100-20200624) Package language: en_US'

# variable length
len=6

# find variable names based on length
for var in $(echo "$text" | grep -oE "[^(0-9:)]{$((len+1)),}" | grep -oE '\S.*' | sed -n 's,\s,.,p')
  do
    # convert substrings and set variables name=value
    eval "$(echo "$text" | grep -oE "$var:\s+\S+" | sed -nr 's,:\s+,=,p' | sed -n 's,\s,_,p')"
done

# print variable info
declare -p | grep -E 'declare -- [A-Za-z]+_\S+='

Note: eval is just used for demonstration. the above code is compatible with (da)sh. in bash you can create array instead of multiple variables