It’s always dangerous for any team to start throwing accusations around about teams fielding weakened teams or not taking a competition seriously.
Essentially you are trying to say that actual professional footballers should be disrespected for being chosen to play for a team, and that’s a slippery slope to go down.
Liverpool were accused of disrespecting The FA Cup when they put out a reserve side against Shrewsbury earlier in the season, but it sounds like the complaint made to the FA has been dismissed:
Shrewsbury CEO Brian Caldwell reveals the FA have dismissed their complaint against #LFC for fielding a weakened team in the FA Cup back in February. League One club claimed it cost them £££ in TV revenue as game wasn't shown live due to Klopp/senior pros not being involved.
— James Pearce (@JamesPearceLFC) June 10, 2020
From a neutral point of view it does seem to be the right decision for two major reasons.
Firstly, Liverpool did put out a team of professional players who are likely paid more than their Shrewsbury counterparts. If they had started putting fans on the pitch then it could be a different matter, but you cannot start kicking off because a professional football team is putting some of their contracted players on the pitch.
Secondly and most importantly, Liverpool actually won the game, so it’s a huge dig against your own team if you complain about the standard of a team that beat you.
Ultimately it will come down to money and it’s understandable that a lower league side will want to make all the cash they can, but they cannot dictate who another team puts on the pitch.