I don't think covid makes this issue any different. Anyone who does anything has to find the motivation to do it. Either it's because you want to do it or your force yourself because it's good for you. But the best motivation is to find a way to do both work and exercise that you actually like to do. So many people force themselves into forms of exercise that they don't like to do, and that's drudgery. Try to find ways of playing if you can instead of always doing something that is isolating and boring to you. Some of us like solitary exercise. Some like to do it in groups. Playing sports is still possible if you do it outdoors with distancing, which you can do with a lot of forms of exercise. If you like what you're doing, you'll look forward to it and won't want to miss it.
I would suggest that Covid makes everything a little more difficult. It seems to throw a psychological dragginess over doing things. So if your exercise routine isn't particularly inspiring, as Pax says, it would not only be hard to stick with in normal times, but to me it seems unsurprising that it would be harder to stick with it now.
I agree that doing something that's a workout in itself but you like, is a good way to exercise. Gardening and cutting up wood are a couple of examples that I've been doing lately. (Weeding can be a satisfying thing to do!) My husband volunteers with "Friends of Trees" and spends Saturdays tromping around in the rain and mud, planting tree seedlings in greenspaces. I volunteer at a primary school, and some days have not sat down once all day. It's not lifting weights, but it's constant walking, and I wouldn't do that if I were home. Maybe along with the workout you have devised, you can add something like this to your week. It can get your juju flowing.