Elections aren’t democracy, as you said democracy is rule by the majority. Pluralism, the ability to choose between parties, isn’t actually democracy either. A single party system can be more democratic if it’s a consultative democracy and reflects the will of the majority, like how it works in China (though China obviously has many, many elections). That also doesn’t mean pluralism is inherently antidemocratic, countries like the DPRK have multiple political parties with seats (even if the majority are held by the WPK), just that the will of the majority be upheld.

In capitalism, a tiny class of people controls the most essential means of production and distribution for society. The state represents their interests, and any parties that exist must represent them, or instead have strong grassroots support and work against the state (such as the Bolsheviks). Choosing between any number of capitalist parties doesn’t mean workers are going to be represented. No western country represents the will of the majority.