Backlog with more than 250 issues has room for improvements in terms of performance

Issue Summary

When Next-gen backlog shows a number of cards greater than 250 cards, the initial load of the backlog will be slower.

Steps to Reproduce

1. Have next-gen project type and create 250+ issues adding them to the backlog
2. Open Next-gen backlog

Expected Results

Next-gen backlog would initially load in a similar time to classic boards with 300 cards

Actual Results

The backlog loads very slow.

Workaround

1. Reduce number of cards on the backlog
2. Switch to Classic projects and migrate issues over