If you want people to be more active in politics,then you have to remove the extensive punishments that people face for being active in politics.
Why don't more people (especially the young) get involved in politics?
Because it is unlikely to do their career chances any good (unless they are a politician), and it is quite likely to cause their career prospects harm.
Peoples political beliefs are part of the way they think about things - to be punished for the way you think make it a 'thought crime' and is a direct attack on free speech.
The solution? Make political beliefs a Protected Characteristic under the Equality Act 2010.
Make it illegal to discriminate based on political beliefs, and where necessary bring in quotas in the public sector and targets in the private sector to ensure all political beliefs are properly represented at all levels of society.
The first impact would (of course) be to install brexit supporters throughout the Civil Service and BBC, removing remainers who have been made redundant.
It would also likely be a improper for employers to search individuals social media and other historic material that does not form part of their current CV - other than to verify the details on the CV (or application form).
If you want people to be more active in politics,then you have to remove the extensive punishments that people face for being active in politics.