LeBron definitely isn't a top-5 player any more; talking strictly about this upcoming season, there are at least 7 players I'd without a doubt take over him (in no particular order): Curry, Durant, Giannis, Embiid, Jokic, Tatum, and Morant. I'd have him somewhere between 8-20, which includes a lot of other offense-only players like Luka Doncic and Trae Young, the not as offensively elite but two-way players like Kawhi and Paul George, and the could be greats that are injury prone and unreliable like AD, Kyrie and Zion. I feel like there's a lot of fluidity ranking the guys in that 2nd tier.
LeBron still has tremendous offensive skills, good offensive efficiency, and has become a better shooter as he's aged...he just hasn't been good defensively with regularity since he returned to Cleveland from Miami, and he's not as reliable anymore. The 2nd Cavs stint he could still play 75 games a year due to coasting defensively, but over the duration of his Lakers tenure he regularly misses 25-30% of the games now due to injuries and rest. He doesn't have nearly the overall impact he used to have on winning between the lack of defense and missing games.
Kyrie Irving isn't a championship contending move for the Lakers. The year they won the much maligned "bubble championship", the Lakers actually had a very good team before the Covid shutdown because Anthony Davis stayed relatively healthy and had a great year, and they actually had quality depth with legitimate role players and a lot of perimeter shooting. The "pause" ensured they got to the playoffs well rested and healthy. Their current roster is very thin on rotational talent (and IMO their best guy in this regard left in free agency), and they'd be very heavily dependent on everything going perfect with that trio if they acquired Kyrie. The value of the trade IMO would be valueless unless they also manage to swindle from Brooklyn an elite shooter in Joe Harris. To me they'd just become at best a very competitive 2nd round team if healthy that would be roadkill if they managed to get to the Western Conference Finals. If Durant gets to the Suns I don't think they'd have any chance of getting out of the second round. They just don't have the talent/depth at the 4th-8th spots on the roster to beat the top 5-6 teams in a playoff series.