There aren't many dates in the calendar where any postponed games can go in ...
As things stand the only THREE available dates till the end of the season are April 4/5 midweek, May 2/3 midweek and May 23/24 midweek just before the final league game weekend.
Those usually are needed anyway for any teams reaching Carabao Cup final ... FA Cup QF, and SF as those three domestic cup games don't have a free PL weekend for them.
That then brings us back to two earmarked mid-weeks in Jan 17/18 (currently for FA Cup R3 replays) and Feb 7/8 (currently for FA Cup R4 replays) ... so in my eyes those two simply need to go. I understand how financially beneficial these can be for smaller or lower league clubs if they were to take a bigger team back home for a replay or even get a share of the replay at bigger team's ground and take fans there ... but there just isn't a place to put them in. Unless we want to have a couple of four games a week SAT-TUE-THU-SUN kind of schedules I really don't see where they place them.
There is one unusual free mid-week for both City and Arsenal ... Feb 14/15 one, when they aren't involved in the Europa League playoffs that week and City's R16 game isn't till the week after ... there are however other CL R16 games going on that mid-week and would require UEFA permission to hold it, which I guess has precedence so should be a possibility specifically for that Arsenal (A) game ... still leaves other games and with 10 games off one weekend postponed where all 20 teams are involved, they really will have to let go of at least one FA Cup replay midweek to place them all (or extend the season by a week - but that's a lot more complex and would mean pushing FA Cup Final into a midweek or play alongside CL final and hope teams in FA Cup final aren't in the CL final as well etc.)
There's currently 14 PL games postponed, 10 from one weekend involving all 20 teams and another 4 means 8 teams need to be sorted (see below) ... a quick look tells me five of those eight all involved in Europe: City, Arsenal, Liverpool, Chelsea and United so it's certainly a challenge finding free slots.
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EDIT: Something else to remember is our home game against Spurs was already picked by Sky and our Arsenal away fixture was an Amazon Prime game ... so both those would retain the TV rights and will be showing them live as and when they're rescheduled for - meaning they'd have a say in when to put them on. Say a mid-week is given and Sky already has other games scheduled for Tue/Wed, they might put us on a Thu to maximize their viewing share that midweek. Same if Amazon wants to put one on the same time when it clashes with BT Sport showing a CL game or Sky another PL game, they can also object to it etc. so it's not as simple as just ok let's put them all on this midweek or that ... and I suspect that's what's causing the delay in slotting these somewhere ... too many people to please at the same time ... and us match going fans as always come last!