USSR was closed off in many ways to “the West” and hence was in an noncompetitive starting point , and second the 90s happened, completely wrecking the country.
Projects tanked, companies flopped, timelines went out the window. Technology stagnated, and to compete in the global market vs giants like Airbus or Boeing, with established support networks, financial muscle…
There were some promising projects in the late 80s and early 90s but events overtook them and they never got a chance to prosper.

Now creating an “all-Russian” globally competitive plane is nonsense of course, but with enough gov support and foreign cooperation the industry can make a reasonable aircraft (SSJ), or even quite a good one (MS-21).