There are only 2 parties with a realistic chance of forming government and winning the seat in a constituency
10 parties in Parliament after the 2019 election is the illusion of choice as on most ballot papers there are only 3 or 4 parties represented, usually with fairly similar policies
Unelected elements
The Monarchy and HOL are not selected to represent any specific sections of society so there is no way of properly holding them to account
There are 92 hereditary peers
Turnout
Low turnout can skew results as it challenges the legitimacy of decisions made as it may be a minority making a decision
Historic low in 2001 of only 59%
West Lothian Question and EVEL (English Votes for English Laws)
Scottish, Welsh, and Northern Ireland MPs can vote on matters that affect only England whereas English MPs cannot vote on matters that affect only a devolved nation
Change in tuition fees was passed only with the votes from Scottish MPs
Pressure groups
They are not all on equal footing and can be quite elitist - they are completely money based and their influence depends on the size of their following
Weakness of the Electoral Commission
They are only reactive - parties can break the rules and they would only face a fine afterwards meaning they can get away with it