Enough resources have already been wasted on them. As for neoantigen based vaccines, they are being given with anti-PD(L)-1 agents, but based on the data  I think they will show much better activity in patients who have had SOC and test positive for ctDNA after (both BNTX/RHBBY & GRTS are going to be doing this) .
In those with advanced disease cell based therapies are going to be a much better option as this approach enables rapid innovation, can build on versions that have been established, minimises systemic toxicities observed with many immunotherapies, may reduce overall costs and should greatly improve the antitumour activity as they can be 'tailored' to combat the complexity of different TMEs.
An example would be AUTL's AUTO7. This CAR-T consists of six transgenes. They are: 1) an anti-PSMA CAR based on a novel humanised binder; 2) a safety switch; 3) dominant negative TGFbRII to induce TGF-b resistance; 4) truncated SHP2 to stop PD-1/CTLA-4/TIGIT/BTLA/2B4 pathway inhibition; 5) a constitutively active cytokine signal (in addition to the 4-1BB co-stim) to improve proliferation and persistence, and finally 6) IL-12 to modulate the suppressive TME by local secretion. Future versions could have a number of other improvements, like this .