In the UK the public overwhelmingly support the age controls, so even political parties who would otherwise oppose it just stay silent, because the public narrative
You have to shift the narrative. Farage does this - he's finally after 20 years managed to get elected to parliament, he's head of a company with 4 MPs, same say as the Greens, about the same as the nationalists, yet for 20 years he has steered the conversation and got what he wants time after time
The electoral system has been working against him. At the last general election Reform got a larger share of the vote than the Lib Dems, yet the result is that they got 5 MPs while the Lib Dems got 72.
The Brexit referendum and the current national polls that put Reform in first place at 27% (YouGov) show that they are not just "steering the conversation". When people's concerns keep being ignored at one point someone will come up to fill this "gap in the market", this is legitimate and how democracy works.
Actual election results:
2010: 3%
2015: 13%. He was the only party to endorse leaving the EU in that election.
2016: (52% vote to leave the EU)
2017: retired
2019: 2%
2024: 14%
Yet his prime policy was passed in 2016 and implemented in 2019.
You don't need people to vote for you to get your policies passed. You need people to just believe in what you say, and other politicians will see that and implement them. The most successful politicians see all sides "steal their policies" and implement them. That's assuming your goal is the policy, not the power.