A big Stadium doesn't qualify a club as successful, its merely a means to bring money into the club if the location is right and the interest is their from supporters to corporate sponsors alike. And I mention the latter because they will be investing in the club sufficiently to justify filling sections of the ground with plastic fans to bring in revenue.
Essentially a large stadium these days is a statement of importance but it doesn't always pay dividends. Coventry got fucked up the arse over the Ricoh arena, the Stadio Delle Alpi was widely unpopular and fans didn't pack it out for Juve and for West Ham the Olympic Stadium just isn't fit for purpose.
Which as tangential as that all is, if Liverpool want a bigger ground it's either about money or it's not and it's about getting true fans to games because supply and demand will allow the club to charge through the nose for tickets.