At the point of the 2019 election stopping Brexit wasn't really on the table - no major party was against it. Labour had a vague message that was not anti-Brexit. Lib Dems may have technically been anti-Brexit but have no trust (is "no Brexit" the same as "no tuition fees"?) and have fewer seats than even the SNP (oh and their leader lost her seat).
The public were basically given no choice in 2019