Selling Walcott and buying Lozano would be expensive and risky. You also don't just forget Richy can play both left and right.
We have bigger issues than a marginal increase of indeed Chucky is better than Walcott.
I don't think Lozano would represent a huge risk, if brands identified him as a player he believes could comfortably adapt to this league then so far anyway he seems to be getting those decisions spot on, having recruited him previously and him doing brilliantly when first arriving in Europe, then you'd have to say it looks a high likelihood it'd be a smart purchase.
Is he an improvement over Walcott, I'd say he has 8/9 years on his side, and whilst he may have his own flaws we aren't aware of not watching him every week, one thing is certain, at his age those flaws can be worked on and the player can be massively improved - Walcott is what he is, his flaws won't go away at his age, he's pretty inconsistent, injury prone etc.
Best scenario we sign lozano who right now is arguably already better than Walcott, and who has the potential to be far better in a few seasons, keep Walcott as a squad option, it's ultimately his level for any team with top 4/6 am itions, and why he spent 10+ years in that exact role at Arsenal.
I'd say a marginal increase in a position is 100% worth it, when that increase comes with a 8/9 years younger player, who fits the system better and who doesn't have the ingrained flaws of the older player.